feat(plex): P2 player — rich full-page HLS/direct player + watch-state

- backend: GET /api/plex/item/{rk} detail (metadata, cast + intro/credit markers
  from Plex, episode prev/next, per-user resume+status); POST /item/{rk}/progress
  (resume checkpoint, near-end→watched) + /state (new|watched|hidden).
- frontend PlexPlayer.tsx (lazy, pulls hls.js): full-page player over the Plex
  module. Direct files stream raw <video>; remux via hls.js on the seek-restart
  session — custom controls map the ABSOLUTE timeline over the session offset, and a
  seek beyond the loaded region restarts the session at the target. Play/pause/resume
  /restart, ±10s seek, prev/next episode (Shift+←/→), volume, windowed/fullscreen,
  full keyboard, Skip intro/Skip credits from markers (shaded on the seekbar),
  auto-advance + watched-on-end, resume from saved position, 10s progress checkpoints.
- PlexBrowse: card/episode click opens the player as a history subview (browser Back
  returns to the grid/show). api client (plexItem/plexSession/plexProgress/plexSetState)
  + types; plex.player.* i18n en/hu/de. hls.js@^1.6.16.
- Verified over HTTP: detail w/ markers+cast+episode-nav, progress persist. Video
  playback itself is pending browser UAT. Subtitle/audio track SELECTION deferred.

frontend/src/lib/api.ts

@@ -672,6 +672,37 @@ export interface PlexShowDetail {
   seasons: PlexSeasonDetail[];
 }
 
+export interface PlexMarker {
+  type: "intro" | "credits";
+  start_s: number;
+  end_s: number;
+}
+export interface PlexItemDetail {
+  id: string;
+  kind: "movie" | "episode";
+  title: string;
+  summary?: string | null;
+  year?: number | null;
+  duration_seconds: number | null;
+  playable: string; // direct | remux | transcode
+  thumb: string;
+  art: string;
+  cast: string[];
+  markers: PlexMarker[];
+  status: string;
+  position_seconds: number;
+  show_title?: string | null;
+  season_number?: number | null;
+  episode_number?: number | null;
+  prev_id?: string | null;
+  next_id?: string | null;
+}
+export interface PlexPlaySession {
+  mode: "direct" | "hls";
+  url: string;
+  start_s: number;
+}
+
 // Admin Users & roles page.
 export interface AdminUserRow {
   id: number;
@@ -1006,6 +1037,23 @@ export const api = {
   },
   plexShow: (id: string): Promise<PlexShowDetail> =>
     req(`/api/plex/show/${encodeURIComponent(id)}`),
+  plexItem: (id: string): Promise<PlexItemDetail> =>
+    req(`/api/plex/item/${encodeURIComponent(id)}`),
+  plexSession: (id: string, start = 0): Promise<PlexPlaySession> =>
+    req(`/api/plex/stream/${encodeURIComponent(id)}/session?start=${Math.max(0, Math.floor(start))}`, {
+      method: "POST",
+    }),
+  plexProgress: (id: string, position_seconds: number, duration_seconds: number): Promise<unknown> =>
+    req(`/api/plex/item/${encodeURIComponent(id)}/progress`, {
+      method: "POST",
+      body: JSON.stringify({ position_seconds, duration_seconds }),
+    }),
+  plexSetState: (id: string, status: "new" | "watched" | "hidden"): Promise<unknown> =>
+    req(`/api/plex/item/${encodeURIComponent(id)}/state`, {
+      method: "POST",
+      body: JSON.stringify({ status }),
+    }),
+  plexStreamFileUrl: (id: string): string => `/api/plex/stream/${encodeURIComponent(id)}/file`,
   plexImageUrl: (id: string, variant?: "thumb" | "art"): string =>
     `/api/plex/image/${encodeURIComponent(id)}${variant === "art" ? "?variant=art" : ""}`,
   // --- admin: users & roles ---