feat: add media folder management from WebUI

- Add media_folders_management config flag (enabled by default)
- Guard folder CRUD endpoints with 403 when management disabled
- Wire up frontend folder add/edit/delete in Settings tab
- Add per-folder availability check (for network shares)
- Show unavailable badge on offline folders in browser view
- Expose management flag via /api/health endpoint
- Add EN/RU locale keys for folder management UI

media_server/static/js/browser.js

@@ -3,7 +3,7 @@
 // ============================================================
 
 import {
-    t, showToast, escapeHtml, closeDialog,
+    t, showToast, showConfirm, escapeHtml, closeDialog,
     SEARCH_DEBOUNCE_MS, EMPTY_SVG_FILE, EMPTY_SVG_FOLDER, emptyStateHtml,
     getAuthHeaders, hasCredentials,
 } from './core.js';
@@ -15,6 +15,7 @@ let currentOffset = 0;
 let itemsPerPage = parseInt(localStorage.getItem('mediaBrowser.itemsPerPage')) || 100;
 let totalItems = 0;
 let mediaFolders = {};
+let managementEnabled = false;
 let viewMode = localStorage.getItem('mediaBrowser.viewMode') || 'grid';
 let cachedItems = null;
 let browserSearchTerm = '';
@@ -33,7 +34,20 @@ export async function loadMediaFolders() {
 
         if (!response.ok) throw new Error('Failed to load folders');
 
-        mediaFolders = await response.json();
+        const data = await response.json();
+        mediaFolders = data.folders || {};
+        managementEnabled = data.management_enabled || false;
+
+        // Show/hide the media folders settings section
+        const section = document.getElementById('mediaFoldersSection');
+        if (section) {
+            section.style.display = managementEnabled ? '' : 'none';
+        }
+
+        // Render folders table in settings if management is enabled
+        if (managementEnabled) {
+            loadFoldersTable();
+        }
 
         // Load last browsed path or show root folder list
         loadLastBrowserPath();
@@ -78,32 +92,39 @@ function showRootFolders() {
 
     Object.entries(mediaFolders).forEach(([id, folder]) => {
         if (!folder.enabled) return;
+        const unavailable = folder.available === false;
+        const unavailableClass = unavailable ? ' unavailable' : '';
 
         if (viewMode === 'list') {
             const row = document.createElement('div');
-            row.className = 'browser-list-item';
-            row.onclick = () => {
-                currentFolderId = id;
-                browsePath(id, '');
-            };
+            row.className = 'browser-list-item' + unavailableClass;
+            if (!unavailable) {
+                row.onclick = () => {
+                    currentFolderId = id;
+                    browsePath(id, '');
+                };
+            }
             row.innerHTML = `
                 <div class="browser-list-icon">\u{1F4C1}</div>
-                <div class="browser-list-name">${folder.label}</div>
+                <div class="browser-list-name">${escapeHtml(folder.label)}${unavailable ? ' <span class="folder-unavailable-badge">' + t('browser.unavailable') + '</span>' : ''}</div>
             `;
             container.appendChild(row);
         } else {
             const card = document.createElement('div');
-            card.className = 'browser-item';
-            card.onclick = () => {
-                currentFolderId = id;
-                browsePath(id, '');
-            };
+            card.className = 'browser-item' + unavailableClass;
+            if (!unavailable) {
+                card.onclick = () => {
+                    currentFolderId = id;
+                    browsePath(id, '');
+                };
+            }
             card.innerHTML = `
                 <div class="browser-thumb-wrapper">
                     <div class="browser-icon">\u{1F4C1}</div>
                 </div>
                 <div class="browser-item-info">
-                    <div class="browser-item-name">${folder.label}</div>
+                    <div class="browser-item-name">${escapeHtml(folder.label)}</div>
+                    ${unavailable ? '<div class="browser-item-meta folder-unavailable-badge">' + t('browser.unavailable') + '</div>' : ''}
                 </div>
             `;
             container.appendChild(card);
@@ -845,10 +866,72 @@ function loadLastBrowserPath() {
     }
 }
 
-// Folder Management
-export function showManageFoldersDialog() {
-    // TODO: Implement folder management UI
-    showToast(t('browser.manage_folders_hint'), 'info');
+// Folder Management — Settings table
+
+export function loadFoldersTable() {
+    const tbody = document.getElementById('foldersTableBody');
+    if (!tbody) return;
+
+    const entries = Object.entries(mediaFolders);
+    if (entries.length === 0) {
+        tbody.innerHTML = `<tr><td colspan="5" class="empty-state">
+            <div class="empty-state-illustration">
+                <svg viewBox="0 0 64 64"><path d="M8 16h20l4-6h20a4 4 0 014 4v36a4 4 0 01-4 4H8a4 4 0 01-4-4V20a4 4 0 014-4z"/><path d="M4 24h56" stroke-dasharray="4 3" opacity="0.4"/></svg>
+                <p data-i18n="browser.folders_empty">${t('browser.folders_empty')}</p>
+            </div></td></tr>`;
+        return;
+    }
+
+    tbody.innerHTML = entries.map(([id, folder]) => {
+        const available = folder.available !== false;
+        const statusIcon = available
+            ? '<span class="status-dot status-online" title="' + t('browser.folder_available') + '"></span>'
+            : '<span class="status-dot status-offline" title="' + t('browser.folder_unavailable') + '"></span>';
+        const enabledBadge = folder.enabled
+            ? ''
+            : ' <span class="folder-disabled-badge">' + t('browser.folder_disabled') + '</span>';
+        return `<tr>
+            <td>${escapeHtml(id)}${enabledBadge}</td>
+            <td>${escapeHtml(folder.label)}</td>
+            <td class="path-cell" title="${escapeHtml(folder.path)}">${escapeHtml(folder.path)}</td>
+            <td>${statusIcon}</td>
+            <td class="actions-cell">
+                <button class="btn-icon" data-action="edit" data-folder-id="${escapeHtml(id)}" title="${t('browser.folder_edit')}">
+                    <svg viewBox="0 0 24 24" width="16" height="16"><path fill="currentColor" d="M3 17.25V21h3.75L17.81 9.94l-3.75-3.75L3 17.25zM20.71 7.04c.39-.39.39-1.02 0-1.41l-2.34-2.34c-.39-.39-1.02-.39-1.41 0l-1.83 1.83 3.75 3.75 1.83-1.83z"/></svg>
+                </button>
+                <button class="btn-icon btn-danger-icon" data-action="delete" data-folder-id="${escapeHtml(id)}" title="${t('browser.folder_delete')}">
+                    <svg viewBox="0 0 24 24" width="16" height="16"><path fill="currentColor" d="M6 19c0 1.1.9 2 2 2h8c1.1 0 2-.9 2-2V7H6v12zM19 4h-3.5l-1-1h-5l-1 1H5v2h14V4z"/></svg>
+                </button>
+            </td>
+        </tr>`;
+    }).join('');
+}
+
+export function showAddFolderDialog() {
+    document.getElementById('folderDialogTitle').textContent = t('browser.folder_dialog.title_add');
+    document.getElementById('folderIsEdit').value = '';
+    document.getElementById('folderOriginalId').value = '';
+    document.getElementById('folderId').value = '';
+    document.getElementById('folderId').disabled = false;
+    document.getElementById('folderLabel').value = '';
+    document.getElementById('folderPath').value = '';
+    document.getElementById('folderEnabled').checked = true;
+    document.getElementById('folderDialog').showModal();
+}
+
+export function showEditFolderDialog(folderId) {
+    const folder = mediaFolders[folderId];
+    if (!folder) return;
+
+    document.getElementById('folderDialogTitle').textContent = t('browser.folder_dialog.title_edit');
+    document.getElementById('folderIsEdit').value = '1';
+    document.getElementById('folderOriginalId').value = folderId;
+    document.getElementById('folderId').value = folderId;
+    document.getElementById('folderId').disabled = true;
+    document.getElementById('folderLabel').value = folder.label;
+    document.getElementById('folderPath').value = folder.path;
+    document.getElementById('folderEnabled').checked = folder.enabled;
+    document.getElementById('folderDialog').showModal();
 }
 
 export function closeFolderDialog() {
@@ -857,5 +940,90 @@ export function closeFolderDialog() {
 
 export async function saveFolder(event) {
     event.preventDefault();
-    closeFolderDialog();
+
+    const isEdit = document.getElementById('folderIsEdit').value === '1';
+    const folderId = isEdit
+        ? document.getElementById('folderOriginalId').value
+        : document.getElementById('folderId').value.trim();
+    const label = document.getElementById('folderLabel').value.trim();
+    const path = document.getElementById('folderPath').value.trim();
+    const enabled = document.getElementById('folderEnabled').checked;
+
+    if (!folderId || !label || !path) return;
+
+    const submitBtn = document.querySelector('#folderForm button[type="submit"]');
+    if (submitBtn) submitBtn.disabled = true;
+
+    try {
+        let response;
+        if (isEdit) {
+            response = await fetch(`/api/browser/folders/update/${encodeURIComponent(folderId)}`, {
+                method: 'PUT',
+                headers: { 'Content-Type': 'application/json', ...getAuthHeaders() },
+                body: JSON.stringify({ label, path, enabled }),
+            });
+        } else {
+            response = await fetch('/api/browser/folders/create', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json', ...getAuthHeaders() },
+                body: JSON.stringify({ folder_id: folderId, label, path, enabled }),
+            });
+        }
+
+        if (response.ok) {
+            closeFolderDialog();
+            showToast(t(isEdit ? 'browser.folder_updated' : 'browser.folder_created'), 'success');
+            await loadMediaFolders();
+        } else {
+            const result = await response.json().catch(() => ({}));
+            showToast(result.detail || t('browser.folder_save_error'), 'error');
+        }
+    } catch (error) {
+        console.error('Error saving folder:', error);
+        showToast(t('browser.folder_save_error'), 'error');
+    } finally {
+        if (submitBtn) submitBtn.disabled = false;
+    }
+}
+
+export async function deleteFolderConfirm(folderId) {
+    if (!await showConfirm(t('browser.folder_confirm_delete', { name: folderId }))) {
+        return;
+    }
+
+    try {
+        const response = await fetch(`/api/browser/folders/delete/${encodeURIComponent(folderId)}`, {
+            method: 'DELETE',
+            headers: getAuthHeaders(),
+        });
+
+        if (response.ok) {
+            showToast(t('browser.folder_deleted'), 'success');
+            await loadMediaFolders();
+        } else {
+            const result = await response.json().catch(() => ({}));
+            showToast(result.detail || t('browser.folder_delete_error'), 'error');
+        }
+    } catch (error) {
+        console.error('Error deleting folder:', error);
+        showToast(t('browser.folder_delete_error'), 'error');
+    }
+}
+
+// Legacy stub — now handled via settings table
+export function showManageFoldersDialog() {
+    if (managementEnabled) {
+        // Switch to settings tab and scroll to the folders section
+        const switchTabFn = window.switchTab;
+        if (switchTabFn) switchTabFn('settings');
+        setTimeout(() => {
+            const section = document.getElementById('mediaFoldersSection');
+            if (section) {
+                section.setAttribute('open', '');
+                section.scrollIntoView({ behavior: 'smooth' });
+            }
+        }, 100);
+    } else {
+        showToast(t('browser.manage_folders_hint'), 'info');
+    }
 }