feat(dashboard): TMDB trending rail and hero enrichment (backdrop, badges, S/E)

Two dashboard additions, both async after first paint so the page renders
exactly as fast as before:

Trending rail ("Trending this week", dashboardRails.tmdbTrending toggle,
default on, rendered only when TMDB is opted in AND the Electron DB
worker is available):
- TmdbTrendingService fetches /trending/{movie,tv}/week (one request
  each, cached one day per language in tmdb_metadata under
  trending:week), merges by popularity; exposed via the enrichment
  facade (getTrendingWeek)
- DashboardTrendingService matches the titles against imported Xtream
  playlists with ONE batched DB_MATCH_TITLES request, applying the same
  two-tier + year-compatibility rule as actor pages; matched cards show
  the playlist name and navigate straight to the detail view, unmatched
  cards open the global search prefilled (?q=)
- The load fires only after the dashboard's own recent/favorites data
  is in (never competes for the worker at startup) and once per session
- DashboardRailCard gained optional queryParams for the search links

Hero enrichment:
- DashboardHeroTmdbService patches the hero with a TMDB backdrop (only
  when the item has none), a rating badge and up to two genre chips —
  via the enrichment facade, so previously opened items resolve from
  the SQLite cache without network; memoized per title per session,
  staleness-guarded against hero changes in flight
- Series heroes show the tracked "S{n}·E{n}" badge from the playback
  position; the watch-progress bar no longer applies to live heroes

Settings: new dashboardRails.tmdbTrending toggle in Settings > Dashboard.
i18n: 3 new keys translated into all 17 locales via tools/i18n patches.

Tests: dashboard-trending.service.spec.ts (gating, matching, year guard,
single-flight); settings fixtures updated. Docs updated
(tmdb-metadata-enrichment.md Dashboard Integration section, CLAUDE.md).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/web/src/app/settings/settings-dashboard-section.component.html

@@ -160,5 +160,23 @@
                 ></mat-checkbox>
             </div>
         </div>
+
+        <div class="setting-item">
+            <div class="setting-item__meta">
+                <h4>{{ 'SETTINGS.DASHBOARD_RAIL_TMDB_TRENDING' | translate }}</h4>
+                <p>
+                    {{
+                        'SETTINGS.DASHBOARD_RAIL_TMDB_TRENDING_DESCRIPTION'
+                            | translate
+                    }}
+                </p>
+            </div>
+            <div class="setting-item__control setting-item__toggle">
+                <mat-checkbox
+                    formControlName="tmdbTrending"
+                    data-test-id="toggle-dashboard-rail-tmdb-trending"
+                ></mat-checkbox>
+            </div>
+        </div>
     </div>
 </section>