refactor(player,epg): add MPV reuse, IPC commands, and EPG handlers

Introduce MPV process reuse and IPC control, and add basic EPG IPC
handlers.

- Add GET_CHANNEL_PROGRAMS and FETCH_EPG ipc handlers to epg.events.ts
  to expose fetching EPG data by channel or URLs.
- Rework player.events.ts:
  - Export proper bootstrap and add module-level mpvProcess and
    mpvSocketPath to track a reusable MPV instance.
  - Add sendMpvCommand helper to communicate with MPV via its IPC socket.
  - Implement OPEN_MPV_PLAYER handler that:
    - Reads MPV path and MPV_REUSE_INSTANCE setting from store.
    - Attempts to reuse an existing MPV process by sending loadfile
      command over the socket when reuse is enabled.
    - Falls back to spawning a new mpv process, creating a unique IPC
      socket path, and storing the process/socket when reuse is enabled.
    - Adds error and exit handlers to clear stored references.
  - Add necessary imports (ChildProcess, existsSync, createConnection).
  - Remove/comment unused import block for shared-interfaces and adapt
    existing code to the new flow.

Why:
- Enable reusing a single MPV instance to improve resource usage and
  provide faster playback switching.
- Add IPC endpoints for EPG to support frontend requests for program
  data.

libs/shared/interfaces/src/lib/ipc-commands.ts

@@ -7,7 +7,8 @@ export const EPG_GET_PROGRAM_DONE = 'EPG:GET_PROGRAM_DONE';
 export const EPG_GET_CHANNELS = 'EPG:GET_CHANNELS';
 export const EPG_GET_CHANNELS_DONE = 'EPG:GET_CHANNELS_DONE';
 export const EPG_GET_CHANNELS_BY_RANGE = 'EPG:EPG_GET_CHANNELS_BY_RANGE';
-export const EPG_GET_CHANNELS_BY_RANGE_RESPONSE = 'EPG:EPG_GET_CHANNELS_BY_RANGE_RESPONSE';
+export const EPG_GET_CHANNELS_BY_RANGE_RESPONSE =
+    'EPG:EPG_GET_CHANNELS_BY_RANGE_RESPONSE';
 export const EPG_FORCE_FETCH = 'EPG:EPG_FORCE_FETCH';
 
 // Playlist related commands
@@ -34,6 +35,7 @@ export const AUTO_UPDATE_PLAYLISTS_RESPONSE = 'AUTO_UPDATE_RESPONSE';
 // Experimental
 export const OPEN_MPV_PLAYER = 'OPEN_MPV_PLAYER';
 export const SET_MPV_PLAYER_PATH = 'SET_MPV_PLAYER_PATH';
+export const SET_MPV_REUSE_INSTANCE = 'SET_MPV_REUSE_INSTANCE';
 export const OPEN_VLC_PLAYER = 'OPEN_VLC_PLAYER';
 export const SET_VLC_PLAYER_PATH = 'SET_VLC_PLAYER_PATH';