feat: migrate storage from JSON files to SQLite

Replace 22 individual JSON store files with a single SQLite database
(data/ledgrab.db). All entity stores now use BaseSqliteStore backed by
SQLite with WAL mode, write-through caching, and thread-safe access.

- Add Database class with SQLite backup/restore API
- Add BaseSqliteStore as drop-in replacement for BaseJsonStore
- Convert all 16 entity stores to SQLite
- Move global settings (MQTT, external URL, auto-backup) to SQLite
  settings table
- Replace JSON backup/restore with SQLite snapshot backups (.db files)
- Remove partial export/import feature (backend + frontend)
- Update demo seed to write directly to SQLite
- Add "Backup Now" button to settings UI
- Remove StorageConfig file path fields (single database_file remains)

server/src/wled_controller/static/js/features/settings.ts

@@ -419,6 +419,22 @@ export async function saveAutoBackupSettings(): Promise<void> {
     }
 }
 
+export async function triggerBackupNow(): Promise<void> {
+    try {
+        const resp = await fetchWithAuth('/system/auto-backup/trigger', { method: 'POST' });
+        if (!resp.ok) {
+            const err = await resp.json().catch(() => ({}));
+            throw new Error(err.detail || `HTTP ${resp.status}`);
+        }
+        showToast(t('settings.auto_backup.backup_created'), 'success');
+        loadBackupList();
+        loadAutoBackupSettings();
+    } catch (err) {
+        console.error('Backup failed:', err);
+        showToast(t('settings.auto_backup.backup_error') + ': ' + err.message, 'error');
+    }
+}
+
 // ─── Saved backup list ────────────────────────────────────
 
 export async function loadBackupList(): Promise<void> {
@@ -566,76 +582,6 @@ export async function loadApiKeysList(): Promise<void> {
     }
 }
 
-// ─── Partial Export / Import ───────────────────────────────────
-
-export async function downloadPartialExport(): Promise<void> {
-    const storeKey = (document.getElementById('settings-partial-store') as HTMLSelectElement).value;
-    try {
-        const resp = await fetchWithAuth(`/system/export/${encodeURIComponent(storeKey)}`, { timeout: 30000 });
-        if (!resp.ok) {
-            const err = await resp.json().catch(() => ({}));
-            throw new Error(err.detail || `HTTP ${resp.status}`);
-        }
-        const blob = await resp.blob();
-        const disposition = resp.headers.get('Content-Disposition') || '';
-        const match = disposition.match(/filename="(.+?)"/);
-        const filename = match ? match[1] : `ledgrab-${storeKey}.json`;
-
-        const a = document.createElement('a');
-        a.href = URL.createObjectURL(blob);
-        a.download = filename;
-        document.body.appendChild(a);
-        a.click();
-        a.remove();
-        URL.revokeObjectURL(a.href);
-
-        showToast(t('settings.partial.export_success'), 'success');
-    } catch (err) {
-        console.error('Partial export failed:', err);
-        showToast(t('settings.partial.export_error') + ': ' + err.message, 'error');
-    }
-}
-
-export async function handlePartialImportFileSelected(input: HTMLInputElement): Promise<void> {
-    const file = input.files![0];
-    input.value = '';
-    if (!file) return;
-
-    const storeKey = (document.getElementById('settings-partial-store') as HTMLSelectElement).value;
-    const merge = (document.getElementById('settings-partial-merge') as HTMLInputElement).checked;
-    const confirmMsg = merge
-        ? t('settings.partial.import_confirm_merge').replace('{store}', storeKey)
-        : t('settings.partial.import_confirm_replace').replace('{store}', storeKey);
-
-    const confirmed = await showConfirm(confirmMsg);
-    if (!confirmed) return;
-
-    try {
-        const formData = new FormData();
-        formData.append('file', file);
-
-        const url = `${API_BASE}/system/import/${encodeURIComponent(storeKey)}?merge=${merge}`;
-        const resp = await fetch(url, {
-            method: 'POST',
-            headers: { 'Authorization': `Bearer ${apiKey}` },
-            body: formData,
-        });
-
-        if (!resp.ok) {
-            const err = await resp.json().catch(() => ({}));
-            throw new Error(err.detail || `HTTP ${resp.status}`);
-        }
-
-        const data = await resp.json();
-        showToast(data.message || t('settings.partial.import_success'), 'success');
-        settingsModal.forceClose();
-
-    } catch (err) {
-        console.error('Partial import failed:', err);
-        showToast(t('settings.partial.import_error') + ': ' + err.message, 'error');
-    }
-}
-
 // ─── Log Level ────────────────────────────────────────────────
 
 export async function loadLogLevel(): Promise<void> {