fix: comprehensive security, bug, performance, and UI/UX audit

Security
- Default bind 127.0.0.1; first-run bootstrap generates random api_token
  and refuses to bind non-loopback without auth unless explicitly opted in
- Path-traversal hardened: BrowserService.validate_path rejects absolute
  paths, drive letters, UNC, NUL bytes. /api/browser/{play,metadata,
  thumbnail} now require folder_id and a folder-relative path
- Pydantic validators on links: http(s) URLs only, mdi:<slug> icons only
- Scripts/callbacks/links create/update/delete gated by *_management flags
- Strict CSP, X-Frame-Options DENY, Referrer-Policy no-referrer,
  X-Content-Type-Options nosniff
- CORS locked to localhost:<port> + 127.0.0.1:<port> by default; configurable
- config.yaml writes atomic (tmp + os.replace) and 0o600 on POSIX
- Subprocesses spawned in their own process group / new session so timeout
  kills the whole tree (Windows CREATE_NEW_PROCESS_GROUP, POSIX
  start_new_session=True)
- Frontend XSS: monitor name + details escapeHtml'd; power button moved to
  delegated data-action handler; remote MDI SVGs parsed and sanitized
  (strip script/foreignObject/on*/javascript: hrefs) before innerHTML
- All dynamic URL segments now wrapped in encodeURIComponent

Bugs
- WebSocket reconnect: close previous socket before opening new, clear
  ping interval per-socket, clear reconnectTimeout up-front, retry on
  online/visibilitychange, try/catch JSON.parse
- Artwork fetch race: AbortController + generation guard
- _broadcast_after_open: initialize status, swallow per-poll errors,
  background tasks tracked in a strong-ref set with done-callback cleanup
- Audio analyzer: sticky _unavailable flag prevents infinite start/stop
  spin when no loopback device exists; cleared by set_device()
- Volume short-circuit cache invalidated when server reports remote volume
- Browser thumbnail race: per-folder generation counter + isConnected
  checks; aborts in-flight fetches on navigation
- Track-skip uses cached title instead of full WinRT status round-trip

Performance
- Linux MPRIS/pactl and /api/display DDC-CI handlers wrapped in
  asyncio.to_thread so blocking IO never stalls the event loop
- browse_directory moved off the event loop (SMB shares could freeze it)
- Windows status poll caches one asyncio loop per worker thread via
  threading.local instead of new_event_loop/close on every 0.5s tick
- broadcast() serializes JSON once and uses send_text to all clients
- Hourly thumbnail cache cleanup scheduled in lifespan (was never invoked
  — cache grew unbounded)
- Progress drag listeners attached only while dragging

Quality
- All asyncio.get_event_loop() in coroutines → get_running_loop()
- ThreadPoolExecutors shut down cleanly during lifespan teardown
- config_manager dedup: 12 near-identical methods collapsed onto generic
  _upsert/_delete helpers (~290 lines removed)
- Service worker no longer pass-throughs every fetch
- M3U playlist written via NamedTemporaryFile (no fixed-path symlink
  clobber race)
- __version__ now prefers live pyproject.toml in dev checkouts so
  pip install -e . users see the source-of-truth version, not the stale
  package-metadata version baked in at install time

UI/UX (Studio Reference)
- Green leftover focus rings (rgba(29,185,84,...)) all replaced with
  copper accent (rgba(var(--copper-rgb),...))
- Dialogs: square corners, copper top hairline, unified with editorial
  chrome
- .browser-item: transparent with copper hover border (was filled card)
- Audio device select uses var(--sans) instead of generic system font
- Mobile container padding tuned for ≤480px screens
- Breadcrumb home is a real <button> with aria-label; aria-current on root
- i18n: filled display.msg.power_*, execution.*, scripts.params.execute,
  callbacks.empty in both en + ru

media_server/main.py

@@ -63,10 +63,10 @@ async def lifespan(app: FastAPI):
     logger = logging.getLogger(__name__)
     logger.info(f"Media Server starting on {settings.host}:{settings.port}")
 
-    # Log authentication status
+    # Log authentication status — never log full or partial token material.
     if settings.api_tokens:
-        for label, token in settings.api_tokens.items():
-            logger.info(f"API Token [{label}]: {token[:8]}...")
+        labels = ", ".join(settings.api_tokens.keys())
+        logger.info(f"Authentication enabled. Tokens configured: [{labels}]")
     else:
         logger.warning("No API tokens configured — authentication is DISABLED")
 
@@ -87,6 +87,24 @@ async def lifespan(app: FastAPI):
         # Store globally so health endpoint can access cached result
         app.state.update_checker = update_checker
 
+    # Schedule periodic thumbnail cache cleanup so the 500 MB cap is actually
+    # enforced. Runs once at startup and then hourly until shutdown.
+    from .services.thumbnail_service import ThumbnailService
+
+    async def _thumbnail_cleanup_loop() -> None:
+        while True:
+            try:
+                await asyncio.to_thread(ThumbnailService.cleanup_cache)
+            except Exception as e:
+                logger.warning("Thumbnail cache cleanup failed: %s", e)
+            try:
+                await asyncio.sleep(3600)
+            except asyncio.CancelledError:
+                break
+
+    import asyncio
+    cleanup_task = asyncio.create_task(_thumbnail_cleanup_loop())
+
     # Register audio visualizer (capture starts on-demand when clients subscribe)
     analyzer = None
     if settings.visualizer_enabled:
@@ -109,6 +127,13 @@ async def lifespan(app: FastAPI):
     if update_checker is not None:
         await update_checker.stop()
 
+    # Cancel periodic thumbnail cleanup
+    cleanup_task.cancel()
+    try:
+        await cleanup_task
+    except asyncio.CancelledError:
+        pass
+
     # Stop audio visualizer
     await ws_manager.stop_audio_monitor()
     if analyzer and analyzer.running:
@@ -117,6 +142,13 @@ async def lifespan(app: FastAPI):
     # Stop WebSocket status monitor
     await ws_manager.stop_status_monitor()
 
+    # Shut down dedicated thread pools so pending scripts don't leak threads
+    from .routes.callbacks import shutdown_callback_executor
+    from .routes.scripts import shutdown_script_executor
+
+    shutdown_script_executor()
+    shutdown_callback_executor()
+
     # Clean up platform-specific resources
     import platform as _platform
     if _platform.system() == "Windows":
@@ -138,16 +170,43 @@ def create_app() -> FastAPI:
     # Compress responses > 1KB
     app.add_middleware(GZipMiddleware, minimum_size=1000)
 
-    # Add CORS middleware for cross-origin requests
-    # Token auth is via Authorization header, not cookies, so credentials are not needed
+    # CORS — restrict to same-origin by default; users that integrate the API
+    # from another origin (e.g. Home Assistant on a different host) can set
+    # cors_origins in config.yaml.
+    cors_origins = settings.cors_origins or [
+        f"http://localhost:{settings.port}",
+        f"http://127.0.0.1:{settings.port}",
+    ]
     app.add_middleware(
         CORSMiddleware,
-        allow_origins=["*"],
+        allow_origins=cors_origins,
         allow_credentials=False,
-        allow_methods=["*"],
-        allow_headers=["*"],
+        allow_methods=["GET", "POST", "PUT", "DELETE", "OPTIONS"],
+        allow_headers=["Authorization", "Content-Type"],
     )
 
+    # Security headers — strict CSP for the bundled UI, disallow framing, hide referrer.
+    @app.middleware("http")
+    async def security_headers_middleware(request: Request, call_next):
+        response = await call_next(request)
+        response.headers.setdefault(
+            "Content-Security-Policy",
+            (
+                "default-src 'self'; "
+                "img-src 'self' data: blob: https://api.iconify.design; "
+                "connect-src 'self' https://api.iconify.design ws: wss:; "
+                "script-src 'self'; "
+                "style-src 'self' 'unsafe-inline'; "
+                "font-src 'self' data:; "
+                "frame-ancestors 'none'; "
+                "base-uri 'self'"
+            ),
+        )
+        response.headers.setdefault("X-Frame-Options", "DENY")
+        response.headers.setdefault("X-Content-Type-Options", "nosniff")
+        response.headers.setdefault("Referrer-Policy", "no-referrer")
+        return response
+
     # Add token logging middleware
     @app.middleware("http")
     async def token_logging_middleware(request: Request, call_next):
@@ -247,7 +306,8 @@ def main():
     if args.generate_config:
         config_path = generate_default_config()
         print(f"Configuration file generated at: {config_path}")
-        print("Authentication is disabled by default. Add api_tokens to enable it.")
+        print("A random API token was generated under api_tokens.default.")
+        print("Run `python -m media_server.main --show-token` to view it.")
         return
 
     if args.show_token:
@@ -260,6 +320,32 @@ def main():
             print("\nAuthentication is DISABLED (no tokens configured)")
         return
 
+    # First-run bootstrap: if no config has ever been written, generate one
+    # with a random token instead of starting in the insecure "no-auth" mode.
+    config_path = get_config_dir() / "config.yaml"
+    if not config_path.exists() and not settings.api_tokens:
+        try:
+            generate_default_config(config_path)
+            print(
+                f"\nFirst run: generated default config at {config_path}.\n"
+                "Run --show-token to retrieve the API token, then restart.",
+                file=sys.stderr,
+            )
+            sys.exit(0)
+        except OSError as e:
+            print(f"WARNING: could not bootstrap config: {e}", file=sys.stderr)
+
+    # Refuse to bind a non-loopback address with no tokens, unless explicitly opted in.
+    non_loopback = args.host not in ("127.0.0.1", "localhost", "::1")
+    if non_loopback and not settings.api_tokens and not settings.allow_lan_without_auth:
+        print(
+            "ERROR: refusing to bind a non-loopback address with no api_tokens configured.\n"
+            "Either set api_tokens in config.yaml, bind to 127.0.0.1,"
+            " or set allow_lan_without_auth: true in config.yaml to override.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
     # Check if port is available before starting
     with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
         try: