feat: add update-available notification system

- Abstract ReleaseProvider protocol for platform-agnostic version checking
- GiteaReleaseProvider implementation using stdlib urllib
- UpdateChecker service with periodic background checks and WS broadcast
- Persistent dismissible banner in Web UI when a new version is detected
- Health endpoint now returns cached update info
- Configurable via update_check_enabled and update_check_interval settings
- i18n support (EN/RU)

media_server/static/css/styles.css

@@ -3490,6 +3490,59 @@ footer .separator {
     }
 }
 
+/* Update Banner */
+.update-banner {
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    z-index: 1001;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: 12px;
+    padding: 10px 16px;
+    background: var(--accent);
+    color: #fff;
+    font-size: 0.85rem;
+    font-weight: 500;
+    text-align: center;
+    transition: transform 0.3s ease;
+}
+
+.update-banner:not(.hidden) {
+    animation: bannerSlideIn 0.4s ease-out;
+}
+
+.update-banner.hidden {
+    transform: translateY(-100%);
+    pointer-events: none;
+}
+
+.update-banner a {
+    color: #fff;
+    text-decoration: underline;
+    font-weight: 600;
+}
+
+.update-banner a:hover {
+    opacity: 0.85;
+}
+
+.update-banner-close {
+    background: none;
+    color: #fff;
+    font-size: 1.2rem;
+    padding: 0 4px;
+    opacity: 0.7;
+    cursor: pointer;
+    line-height: 1;
+}
+
+.update-banner-close:hover {
+    opacity: 1;
+}
+
 /* Connection Banner */
 .connection-banner {
     position: fixed;

media_server/static/index.html

@@ -114,6 +114,13 @@
             </div>
         </header>
 
+        <!-- Update Banner -->
+        <div class="update-banner hidden" id="updateBanner">
+            <span id="updateBannerText"></span>
+            <a id="updateBannerLink" href="#" target="_blank" rel="noopener noreferrer" data-i18n="update.view_release">View Release</a>
+            <button class="update-banner-close" id="updateBannerClose">&times;</button>
+        </div>
+
         <!-- Connection Banner -->
         <div class="connection-banner hidden" id="connectionBanner">
             <span id="connectionBannerText"></span>

media_server/static/js/core.js

@@ -318,12 +318,35 @@ export async function fetchVersion() {
             if (data.version) {
                 label.textContent = `v${data.version}`;
             }
+            if (data.update_available) {
+                showUpdateBanner(data.update_available);
+            }
         }
     } catch (error) {
         console.error('Error fetching version:', error);
     }
 }
 
+export function showUpdateBanner(update) {
+    const dismissed = sessionStorage.getItem('update_dismissed');
+    if (dismissed === update.latest) return;
+
+    const banner = document.getElementById('updateBanner');
+    const text = document.getElementById('updateBannerText');
+    const link = document.getElementById('updateBannerLink');
+    const closeBtn = document.getElementById('updateBannerClose');
+
+    text.textContent = t('update.available', { version: update.latest });
+    link.href = update.url;
+    link.textContent = t('update.view_release');
+    banner.classList.remove('hidden');
+
+    closeBtn.onclick = () => {
+        banner.classList.add('hidden');
+        sessionStorage.setItem('update_dismissed', update.latest);
+    };
+}
+
 // ============================================================
 // Shared Utilities
 // ============================================================

media_server/static/js/websocket.js

@@ -6,7 +6,7 @@ import {
     dom, t, showToast, setWs,
     WS_BACKOFF_BASE_MS, WS_BACKOFF_MAX_MS,
     WS_MAX_RECONNECT_ATTEMPTS, WS_PING_INTERVAL_MS,
-    authRequired,
+    authRequired, showUpdateBanner,
 } from './core.js';
 import { updateUI, visualizerEnabled, visualizerAvailable, setFrequencyData, stopPositionInterpolation, loadAudioDevices } from './player.js';
 import { loadScripts, loadScriptsTable, displayQuickAccess } from './scripts.js';
@@ -100,6 +100,8 @@ export function connectWebSocket(token) {
             loadHeaderLinks();
             loadLinksTable();
             displayQuickAccess();
+        } else if (msg.type === 'update_available') {
+            showUpdateBanner(msg.data);
         } else if (msg.type === 'audio_data') {
             setFrequencyData(msg.data);
         } else if (msg.type === 'error') {

media_server/static/locales/en.json

@@ -224,5 +224,7 @@
   "links.confirm.delete": "Are you sure you want to delete the link \"{name}\"?",
   "links.confirm.unsaved": "You have unsaved changes. Are you sure you want to discard them?",
   "footer.created_by": "Created by",
-  "footer.source_code": "Source Code"
+  "footer.source_code": "Source Code",
+  "update.available": "Update available: v{version}",
+  "update.view_release": "View Release"
 }

media_server/static/locales/ru.json

@@ -224,5 +224,7 @@
   "links.confirm.delete": "Вы уверены, что хотите удалить ссылку \"{name}\"?",
   "links.confirm.unsaved": "У вас есть несохраненные изменения. Вы уверены, что хотите отменить их?",
   "footer.created_by": "Создано",
-  "footer.source_code": "Исходный код"
+  "footer.source_code": "Исходный код",
+  "update.available": "Доступно обновление: v{version}",
+  "update.view_release": "Перейти к релизу"
 }