fix: resolve 13 review issues across casting components

- casting-player: remove redundant self-navigation useEffect
- casting-player: derive Type from metadata instead of hardcoding 'Movie'
- casting-player: pass null to useTrickplay instead of empty BaseItemDto
- casting-player: use != null for skip time labels (allow 0 to render)
- Chromecast: case-insensitive m3u8 detection via regex
- Chromecast: fix UUID hyphen indices to 4,6,8,10 for proper v4 format
- CastingMiniPlayer: use SeriesPrimaryImageTag for series poster URL
- ChromecastConnectionMenu: send rounded volume to castSession.setVolume
- ChromecastConnectionMenu: use isMutedRef in onValueChange to avoid stale closure
- ChromecastDeviceSheet: skip volume sync during active sliding
- ChromecastDeviceSheet: move unmute logic from onValueChange to onSlidingStart
- useCasting: detect playback start via isPlaying/playerState, not just progress>0
- useCasting: derive isChromecastAvailable from castState instead of hardcoding true
- useTrickplay: accept BaseItemDto|null with null guards on Id access

components/chromecast/ChromecastConnectionMenu.tsx

@@ -108,7 +108,7 @@ export const ChromecastConnectionMenu: React.FC<
 
       try {
         if (castSession) {
-          await castSession.setVolume(value / 100);
+          await castSession.setVolume(rounded / 100);
         }
       } catch (error) {
         console.error("[Connection Menu] Volume error:", error);
@@ -262,7 +262,9 @@ export const ChromecastConnectionMenu: React.FC<
                     onValueChange={async (value) => {
                       volumeValue.value = value;
                       handleVolumeChange(value);
-                      if (isMuted) {
+                      // Unmute when adjusting volume - use ref to avoid
+                      // stale closure and prevent repeated async calls
+                      if (isMutedRef.current) {
                         isMutedRef.current = false;
                         setIsMuted(false);
                         try {