fix: production-readiness hardening — security, perf, a11y, observability

Security
- Default scripts_management, callbacks_management, links_management, and
  media_folders_management to False so a leaked token cannot escalate to RCE
  through admin CRUD endpoints.
- TokenSpec + scope hierarchy (read | control | admin); legacy bare-string
  api_tokens entries promote to admin for back-compat. Management endpoints
  now require admin scope.
- WebSocket subprotocol auth (Sec-WebSocket-Protocol: media-server.token.<T>)
  preferred over ?token= query so the token no longer lands in URL/history/
  Referer; query fallback retained for HA integration back-compat.
- Origin allow-list check on the WS endpoint (CSWSH defence).
- In-process token-bucket rate limiter: 5/min for failed auths,
  10/min for /api/scripts/execute and /api/callbacks/execute.
- shell=False subprocess path (shlex.split) + per-parameter regex `pattern`
  in ScriptParameterConfig to harden shell=true scripts against parameter
  injection (Windows cmd.exe env-var expansion).
- CSP gains form-action, worker-src, manifest-src directives.
- Refuse cors_origins=["*"] at startup; strip token=... from uvicorn access
  logs; validate Gitea release tag against strict SemVer regex.
- noopener noreferrer + no-referrer referrerpolicy on every outbound link.
- icacls hardening of config.yaml on Windows (current user + SYSTEM +
  Administrators only); 0600 still enforced on POSIX.
- WS volume handler clamps input and never drops the socket on bad messages.

Performance
- Album-art read in windows_media gated by track key — was decoding the
  WinRT thumbnail twice per second regardless of track changes.
- /api/media/artwork returns content-derived ETag + Cache-Control so the
  browser sends If-None-Match and gets 304s on track repeats.
- Foreground-service ctypes argtypes hoisted to one-time module init
  (was re-declaring ~14 prototypes per probe).
- display_service _static_cache keyed by (edid_hash, ...) tuple with
  eviction of disappeared monitors — fixes stale capabilities on hot-plug
  swaps where the new topology has the same monitor count.
- Visualizer rAF loop paused on document.hidden, resumed on visible.

Reliability / bug fixes
- Lifespan rewritten as try/yield/finally so a partial-startup failure
  cannot orphan background tasks or executors.
- _run_callback in routes/media.py keeps a strong task ref (GC-safe) and
  uses the dedicated callback executor instead of the default pool.
- macos_media.set_volume() no longer always returns True.
- TrayManager._restart_requested initialised in __init__; set before
  signalling exit so the main thread observes it correctly.
- Missing static_dir now logs a WARNING instead of silent UI disable.

UX / accessibility / PWA
- manifest.json theme_color and background_color match the Studio Reference
  base (#0E0D0B); added id and scope for PWA installability.
- ARIA on mini-player icon buttons; inner SVGs marked aria-hidden.
- OS mediaSession API wired so headset / lockscreen / Bluetooth buttons
  drive play/pause/next/prev/seek and show track metadata + artwork.

Observability
- X-Request-ID middleware (accept upstream id if it matches a safe regex,
  otherwise UUID4); request_id_var added to ContextVars and included in
  every log line alongside the token label.
- Audit log (append-only JSONL) for every script + callback execution,
  including the on_play/on_pause/etc. event callbacks. Background-thread
  writer; queue capped; flushed in lifespan teardown.

Deployment
- proxy_headers + forwarded_allow_ips plumbed through Settings →
  uvicorn.Config for reverse-proxy installs.
- HTTPS support via ssl_certfile + ssl_keyfile (+ optional password);
  startup refuses to launch with only one of the pair set.
- Thumbnail cache moved from project-root .cache to
  %LOCALAPPDATA%/media-server/cache (Windows) and
  $XDG_CACHE_HOME/media-server/thumbnails (POSIX).

Tests
- 35 new tests across auth scopes, rate limiter, browser path traversal
  (../ NUL UNC absolute), script-param validation incl. regex, Gitea tag
  whitelist, config atomic write + POSIX perms. 47 passed / 4 skipped.

media_server/auth.py

@@ -13,6 +13,8 @@ security = HTTPBearer(auto_error=False)
 
 # Context variable to store current request's token label
 token_label_var: ContextVar[str] = ContextVar("token_label", default="unknown")
+# Per-request correlation ID — generated in middleware if upstream didn't send one.
+request_id_var: ContextVar[str] = ContextVar("request_id", default="-")
 
 
 def auth_enabled() -> bool:
@@ -29,12 +31,42 @@ def get_token_label(token: str) -> Optional[str]:
     Returns:
         The label for the token, or None if invalid
     """
-    for label, stored_token in settings.api_tokens.items():
-        if secrets.compare_digest(stored_token, token):
+    for label, spec in settings.api_tokens.items():
+        if secrets.compare_digest(spec.token, token):
             return label
     return None
 
 
+def token_has_scope(label: str, required: str) -> bool:
+    """Whether the token identified by `label` grants `required` scope."""
+    spec = settings.api_tokens.get(label)
+    if spec is None:
+        # Unknown label = no auth or anonymous; treat as full access only
+        # when auth is disabled entirely (matches existing behaviour).
+        return not auth_enabled()
+    return spec.grants(required)
+
+
+def require_scope(scope: str):
+    """Build a FastAPI dependency that enforces the given scope.
+
+    Use as ``Depends(require_scope("admin"))`` on management endpoints. When
+    auth is disabled the dependency is a no-op (anonymous access).
+    """
+
+    async def _checker(label: str = Depends(verify_token)) -> str:
+        if not auth_enabled():
+            return label
+        if not token_has_scope(label, scope):
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail=f"Token '{label}' lacks required scope: {scope}",
+            )
+        return label
+
+    return _checker
+
+
 async def verify_token(
     request: Request,
     credentials: HTTPAuthorizationCredentials = Depends(security),