feat(cache): TMDB image proxy, posters, cache admin API and settings cards

GET /img/tmdb/{size}/{file} ported from MP ImageHelper / fetch_image
(sanitized cache path under DATA_DIR/cache/images, GLOBAL_IMAGE_CACHE
read switch, md5 ETag / 304, day-based cleanup job). Cache module adds
cache.sweep / cache.images_clean jobs and /cache/tmdb, /cache/images
list and clear endpoints. Library list/detail and the search palette
show posters with the neutral placeholder as fallback; metadata settings
get TMDB cache and image cache cards. Runbook docs/runbook/cache.md and
porting notes docs/porting/moviepilot-tmdb-cache.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/contracts/src/organization.ts

@@ -340,6 +340,8 @@ export const LibraryItem = z.object({
   slotCounts: SlotStatusCounts,
   activeDownloads: NonNegInt,
   lastOrganizedAt: Timestamp.nullable(),
+  /** TMDB 海报路径(metadata.posterPath);前端经图片代理显示,没有时显示无彩占位 */
+  posterPath: z.string().nullable().optional(),
 });
 export type LibraryItem = z.infer<typeof LibraryItem>;