Add Radarr/Sonarr links and richer metadata to alert detail

- Thread titleSlug through RadarrMovie/SonarrSeries → MediaEntry →
  AlertCandidate, building a direct mediaUrl server-side at alert
  generation time (RADARR_URL/movie/slug, SONARR_URL/series/slug)
- Alert detail page: single-column full-width layout, metadata chips
  row showing opened/closed dates, media type, and a "View in Radarr/
  Sonarr" external link button when available
- Comments section sits below the full-width overview card

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/radarr.ts

@@ -13,7 +13,7 @@ export async function buildRadarrMap(): Promise<Map<number, MediaEntry>> {
   return new Map(
     movies.map((m) => [
       m.tmdbId,
-      { title: m.title, sizeOnDisk: m.sizeOnDisk, available: m.isAvailable },
+      { title: m.title, titleSlug: m.titleSlug, sizeOnDisk: m.sizeOnDisk, available: m.isAvailable },
     ])
   );
 }