fix(api): KB 首席架構師審查修復 (I1 tags filter + I2 type annotation)

- I1: Repository list_entries 實作 tags JSONB @> 篩選 (之前聲明未實作)
- I2: ORM tags 型別從 list[dict[str, Any]] 修正為 list[str]

首席架構師審查: 87/100
C1 時區(UTC→Taipei) 為既有系統性問題，另開 task 統一遷移

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/api/src/repositories/knowledge_repository.py

@@ -115,6 +115,11 @@ class KnowledgeDBRepository:
         if status:
             query = query.where(KnowledgeEntryRecord.status == status)
             count_query = count_query.where(KnowledgeEntryRecord.status == status)
+        if tags:
+            for tag in tags:
+                tag_filter = KnowledgeEntryRecord.tags.op('@>')(f'["{tag}"]')
+                query = query.where(tag_filter)
+                count_query = count_query.where(tag_filter)
         if q:
             like_q = f"%{q}%"
             filter_cond = or_(