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>

scripts/start-hidden.vbs

@@ -0,0 +1,7 @@
+Set WshShell = CreateObject("WScript.Shell")
+' Get the directory of this script (scripts\), then go up to media-server root
+scriptDir = CreateObject("Scripting.FileSystemObject").GetParentFolderName(WScript.ScriptFullName)
+serverRoot = CreateObject("Scripting.FileSystemObject").GetParentFolderName(scriptDir)
+WshShell.CurrentDirectory = serverRoot
+' Run python completely hidden (0 = hidden, False = don't wait)
+WshShell.Run "python -m media_server.main", 0, False