Backend optimizations, frontend optimizations, and UI design improvements

Backend optimizations:
- GZip middleware for compressed responses
- Concurrent WebSocket broadcast
- Skip status polling when no clients connected
- Deduplicated token validation with caching
- Fire-and-forget HA state callbacks
- Single stat() per browser item
- Metadata caching (LRU)
- M3U playlist optimization
- Autostart setup (Task Scheduler + hidden VBS launcher)

Frontend code optimizations:
- Fix thumbnail blob URL memory leak
- Fix WebSocket ping interval leak on reconnect
- Skip artwork re-fetch when same track playing
- Deduplicate volume slider logic
- Extract magic numbers into named constants
- Standardize error handling with toast notifications
- Cache play/pause SVG constants
- Loading state management for async buttons
- Request deduplication for rapid clicks
- Cache 30+ DOM element references
- Deduplicate volume updates over WebSocket

Frontend design improvements:
- Progress bar seek thumb and hover expansion
- Custom themed scrollbars
- Toast notification accent border strips
- Keyboard focus-visible states
- Album art ambient glow effect
- Animated sliding tab indicator
- Mini-player top progress line
- Empty state SVG illustrations
- Responsive tablet breakpoint (601-900px)
- Horizontal player layout on wide screens (>900px)
- Glassmorphism mini-player with backdrop blur
- Vinyl spin animation (toggleable)
- Table horizontal scroll on narrow screens

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

media_server/static/locales/en.json

@@ -21,6 +21,7 @@
   "player.title_unavailable": "Title unavailable",
   "player.source": "Source:",
   "player.unknown_source": "Unknown",
+  "player.vinyl": "Vinyl mode",
   "state.playing": "Playing",
   "state.paused": "Paused",
   "state.stopped": "Stopped",
@@ -65,6 +66,10 @@
   "scripts.msg.load_failed": "Failed to load script details",
   "scripts.msg.list_failed": "Failed to load scripts",
   "scripts.confirm.delete": "Are you sure you want to delete the script \"{name}\"?",
+  "scripts.execution.title": "Execution Result",
+  "scripts.execution.output": "Output",
+  "scripts.execution.error_output": "Error Output",
+  "scripts.execution.close": "Close",
   "scripts.confirm.unsaved": "You have unsaved changes. Are you sure you want to discard them?",
   "callbacks.management": "Callback Management",
   "callbacks.description": "Callbacks are scripts triggered automatically by media control events (play, pause, stop, etc.)",
@@ -148,5 +153,7 @@
   "browser.folder_dialog.path_help": "Absolute path to media directory",
   "browser.folder_dialog.enabled": "Enabled",
   "browser.folder_dialog.cancel": "Cancel",
-  "browser.folder_dialog.save": "Save"
+  "browser.folder_dialog.save": "Save",
+  "footer.created_by": "Created by",
+  "footer.source_code": "Source Code"
 }