fix(player): R5 S3 — fullscreen controls, volume memory, Ctrl+wheel zoom

- the interaction overlay yields fully in fullscreen: YouTube only reveals its
  control bar while the iframe itself sees the mouse, so after pressing F the
  native fullscreen button was unreachable
- remember the volume per account (a YT.Player is created per video and always
  starts at 100), plus ArrowUp/ArrowDown volume keys that work in fullscreen
- Ctrl/Cmd+wheel falls through to the browser's zoom instead of the volume

frontend/src/lib/storage.ts

@@ -50,6 +50,9 @@ export const LS = {
   plexQ: "siftlode.plexQ",
   plexPlaylistLayout: "siftlode.plexPlaylistLayout",
   plexPlayerPrefs: "siftlode.plexPlayerPrefs",
+  // The YouTube modal player's volume/mute. A YT.Player instance is created per video and starts
+  // at full volume, so without this every next video is loud again (same idea as plexPlayerPrefs).
+  ytPlayerPrefs: "siftlode.ytPlayerPrefs",
   notifHistory: "siftlode.notifications",
   notifSettings: "siftlode.notifSettings",
   onboardingDismissed: "siftlode.onboarding.dismissed",