Update Web UI: Header redesign, thumbnail fix, and title fallback

- Add version label next to Media Server header (fetched from /api/health)
- Move connection status dot before title, remove status text
- Move logout button into header after language selector
- Return 204 instead of 404 for missing thumbnails (eliminates console errors)
- Show "Title unavailable" when media is playing but title is empty
- Add player.title_unavailable translation key for en/ru locales

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

media_server/static/css/styles.css

@@ -72,12 +72,14 @@
             font-weight: 600;
         }
 
-        .status-indicator {
-            display: flex;
-            align-items: center;
-            gap: 0.5rem;
-            font-size: 0.875rem;
-            color: var(--text-secondary);
+        .version-label {
+            font-size: 0.7rem;
+            color: var(--text-muted);
+            background: var(--bg-tertiary);
+            padding: 0.15rem 0.5rem;
+            border-radius: 1rem;
+            font-weight: 500;
+            align-self: center;
         }
 
         .status-dot {
@@ -837,21 +839,24 @@
         }
 
         .clear-token-btn {
-            position: fixed;
-            top: 1rem;
-            right: 1rem;
             width: auto;
             height: auto;
-            padding: 0.5rem 1rem;
+            padding: 6px 12px;
             border-radius: 6px;
-            font-size: 0.75rem;
+            font-size: 14px;
+            font-weight: 500;
             background: var(--bg-tertiary);
+            color: var(--text-secondary);
+            border: 1px solid var(--border);
+            cursor: pointer;
             opacity: 0.7;
         }
 
         .clear-token-btn:hover {
             opacity: 1;
             background: var(--error);
+            color: var(--text-primary);
+            border-color: var(--error);
         }
 
         /* Mini Player (Sticky) */