feat(identity): content unit data hygiene — specials, provisional promotion, duplicate merge (DH-1)

- metadata.includeSpecials (default true): full refresh and the language
  backfill fetch TMDB season 0 (specials) when present, like MP; season 0
  stays out of the episode-total ledger
- refreshMetadata promotes provisional season/episode units that match the
  TMDB season/episode layout to confirmed (source=tmdb), keeping ids and all
  references; non-matching units stay provisional
- content_unit.source (migration 0053): release / file / tmdb / user
- duplicate units (same entity/kind/season/episode/content type/segment) are
  merged as a refresh step and via `scripts/identity-cleanup.ts
  --merge-duplicates` (dry-run by default); keeper = most referenced, then
  confirmed, then earliest; references auto-discovered via FKs and repointed
- ensureUnits takes a per-unit advisory xact lock to stop concurrent lazy
  creation from producing duplicates
- runbooks updated; user DB read-only dry-run: 征途 S01E09/E10 4 units each
  -> 1 each (6 removed), not applied

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

packages/contracts/src/content.ts

@@ -60,6 +60,9 @@ export const Segment = z.enum(["full", "upper", "middle", "lower", "unknown"]);
 export type Segment = z.infer<typeof Segment>;
 export const ContentUnitStatus = z.enum(["provisional", "confirmed", "retired"]);
 export type ContentUnitStatus = z.infer<typeof ContentUnitStatus>;
+/** 内容单元来源(DH-1):资源解析懒建 / 整理·文件懒建 / 按 TMDB 季集结构建或对上后转正式 / 人工;旧行为 null */
+export const ContentUnitSource = z.enum(["release", "file", "tmdb", "user"]);
+export type ContentUnitSource = z.infer<typeof ContentUnitSource>;
 
 /** 季总集数来源:tmdb 元数据 / 插件注入(只升)/ 人工锁定 / 回退被已覆盖最高集兜住 / 沿用 */
 export const EpisodeTotalSource = z.enum(["tmdb", "injected", "manual", "covered_floor", "previous"]);
@@ -89,6 +92,7 @@ export const ContentUnit = EntityBase.extend({
   /** 人工锁定总集数:元数据刷新与注入不再改写 */
   episodeTotalLocked: z.boolean(),
   episodeTotalAt: Timestamp.nullable(),
+  source: ContentUnitSource.nullable(),
 });
 export type ContentUnit = z.infer<typeof ContentUnit>;
 export const ContentUnitCreate = ContentUnit.omit(SERVER_MANAGED).partial({
@@ -109,6 +113,7 @@ export const ContentUnitCreate = ContentUnit.omit(SERVER_MANAGED).partial({
   episodeTotalSource: true,
   episodeTotalLocked: true,
   episodeTotalAt: true,
+  source: true,
 });
 export type ContentUnitCreate = z.infer<typeof ContentUnitCreate>;
 export const ContentUnitUpdate = ContentUnitCreate.omit({ mediaEntityId: true }).partial();