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/routes/display.py

@@ -1,5 +1,6 @@
 """Display brightness, power, contrast, input-source, color-preset and picture-mode API."""
 
+import asyncio
 import logging
 
 from fastapi import APIRouter, Depends
@@ -45,19 +46,21 @@ class PictureModeRequest(BaseModel):
     code: int = Field(ge=0, le=255)
 
 
+# DDC/CI hardware writes open a per-monitor handle and can take seconds —
+# every public endpoint dispatches into a worker thread so the event loop
+# stays responsive.
+
+
 @router.get("/monitors")
 async def get_monitors(
     refresh: bool = False,
     rediscover: bool = False,
     _: str = Depends(verify_token),
 ) -> list[dict]:
-    """List all connected monitors with their reported DDC/CI capabilities.
-
-    - `refresh=true` bypasses the response TTL cache (re-reads current state).
-    - `rediscover=true` also drops the per-monitor capability cache, forcing
-      a full DDC/CI capability probe. Use after a monitor hot-swap.
-    """
-    monitors = list_monitors(force_refresh=refresh, rediscover=rediscover)
+    """List all connected monitors with their reported DDC/CI capabilities."""
+    monitors = await asyncio.to_thread(
+        list_monitors, force_refresh=refresh, rediscover=rediscover
+    )
     logger.debug("Found %d monitors", len(monitors))
     return [m.to_dict() for m in monitors]
 
@@ -67,7 +70,7 @@ async def set_monitor_brightness(
     monitor_id: int, request: BrightnessRequest, _: str = Depends(verify_token)
 ) -> dict:
     """Set brightness for a specific monitor."""
-    success = set_brightness(monitor_id, request.brightness)
+    success = await asyncio.to_thread(set_brightness, monitor_id, request.brightness)
     if success:
         logger.info("Set monitor %d brightness to %d", monitor_id, request.brightness)
     return {"success": success}
@@ -79,7 +82,7 @@ async def set_monitor_power(
 ) -> dict:
     """Turn a monitor on or off."""
     action = "on" if request.on else "off"
-    success = set_power(monitor_id, request.on)
+    success = await asyncio.to_thread(set_power, monitor_id, request.on)
     if success:
         logger.info("Set monitor %d power %s", monitor_id, action)
     return {"success": success}
@@ -90,7 +93,7 @@ async def set_monitor_contrast(
     monitor_id: int, request: ContrastRequest, _: str = Depends(verify_token)
 ) -> dict:
     """Set DDC/CI contrast for a specific monitor."""
-    success = set_contrast(monitor_id, request.contrast)
+    success = await asyncio.to_thread(set_contrast, monitor_id, request.contrast)
     if success:
         logger.info("Set monitor %d contrast to %d", monitor_id, request.contrast)
     return {"success": success}
@@ -101,7 +104,7 @@ async def set_monitor_input_source(
     monitor_id: int, request: InputSourceRequest, _: str = Depends(verify_token)
 ) -> dict:
     """Switch a monitor's DDC/CI input source (e.g. HDMI1, DP1)."""
-    success = set_input_source(monitor_id, request.source)
+    success = await asyncio.to_thread(set_input_source, monitor_id, request.source)
     if success:
         logger.info("Set monitor %d input source to %s", monitor_id, request.source)
     return {"success": success}
@@ -112,7 +115,7 @@ async def set_monitor_color_preset(
     monitor_id: int, request: ColorPresetRequest, _: str = Depends(verify_token)
 ) -> dict:
     """Apply a DDC/CI color preset (color temperature) to the monitor."""
-    success = set_color_preset(monitor_id, request.preset)
+    success = await asyncio.to_thread(set_color_preset, monitor_id, request.preset)
     if success:
         logger.info("Set monitor %d color preset to %s", monitor_id, request.preset)
     return {"success": success}
@@ -123,7 +126,7 @@ async def set_monitor_picture_mode(
     monitor_id: int, request: PictureModeRequest, _: str = Depends(verify_token)
 ) -> dict:
     """Apply a DDC/CI picture/scene mode (VCP 0xDC) by raw code."""
-    success = set_picture_mode(monitor_id, request.code)
+    success = await asyncio.to_thread(set_picture_mode, monitor_id, request.code)
     if success:
         logger.info("Set monitor %d picture mode to code %d", monitor_id, request.code)
     return {"success": success}