Add Radarr discovery + tighten arr sync filters

- playback_aware_radarr_discovery.sh: new two-stage movie discovery
  using recently watched Emby movies as seeds and TMDB recommendations
  as the similarity engine; scores on recency + rating + vote count;
  adds HOST*_TMDB_API_KEY alias to detect_hosts() in common.sh

- emby_to_sonarr_sync.sh: restrict to SONARR_EMBY_LIBRARIES allowlist
  (Anime, Kids Shows, Stand-Up Comedy, TV shows) — excludes Youtube
  and Recorded Sports libraries; add garbage title filter for multi-
  season folder names (S01-S03) and bare bracket tags ([Prof])

- emby_to_radarr_sync.sh: add _is_episode_title filter to block anime
  episode files stored in Movies library (underscore/dot patterns,
  fansub bracket format, episode markers, codec metadata strings)

- emby_to_lidarr_sync.sh: add U+FFFD Unicode replacement character
  filter alongside the existing ASCII ? filter for encoding corruption

- master.conf: RADARR_DISCOVERY_* settings, SONARR/RADARR_EMBY_LIBRARIES
  allowlists, Radarr discovery added to WEEKLY_MAINTENANCE_SCRIPTS

common.sh

@@ -519,6 +519,7 @@ detect_hosts() {
     LIDARR_MUSIC_ROOT_VAR="${MY_ID}_LIDARR_MUSIC_ROOT"; LIDARR_MUSIC_ROOT="${!LIDARR_MUSIC_ROOT_VAR:-}"
     FANART_API_KEY_VAR="${MY_ID}_FANART_API_KEY"; FANART_API_KEY="${!FANART_API_KEY_VAR:-}"
     LASTFM_API_KEY_VAR="${MY_ID}_LASTFM_API_KEY"; LASTFM_API_KEY="${!LASTFM_API_KEY_VAR:-}"
+    TMDB_API_KEY_VAR="${MY_ID}_TMDB_API_KEY";     TMDB_API_KEY="${!TMDB_API_KEY_VAR:-}"
 
     SONARR_URL_VAR="${MY_ID}_SONARR_URL";       SONARR_URL="${!SONARR_URL_VAR:-}"
     SONARR_API_KEY_VAR="${MY_ID}_SONARR_API_KEY"; SONARR_API_KEY="${!SONARR_API_KEY_VAR:-}"