feat(api): Knowledge Base Phase 1 後端四層架構

- models/knowledge.py: Pydantic Schema (EntryType/Source/Status/CRUD)
- db/models.py: KnowledgeEntryRecord ORM (PostgreSQL)
- repositories/interfaces.py: IKnowledgeRepository Protocol
- repositories/knowledge_repository.py: PostgreSQL CRUD 實作
- services/knowledge_service.py: 業務邏輯 (get_db_context 內部管理 session)
- api/v1/knowledge.py: REST Router (get_knowledge_service，無直接 DB 存取)
- main.py: 掛載 Knowledge Base Router
- k8s/jobs/migrate-knowledge-entries.yaml: DB Migration Job

API 端點: GET/POST / | GET/PATCH/DELETE /{id} | POST /{id}/approve
         GET /search | GET /categories

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

apps/api/src/services/knowledge_service.py

@@ -0,0 +1,134 @@
+"""
+Knowledge Service - 業務邏輯層
+===============================
+Knowledge Base Phase 1: CRUD + 狀態流轉 + 搜尋
+
+建立時間: 2026-04-02 (台北時區)
+建立者: Claude Code (Knowledge Base Phase 1)
+
+遵循 leWOOOgo 積木化原則:
+- Service 層封裝業務邏輯
+- 依賴 IKnowledgeRepository Protocol
+- Router 層禁止直接存取 DB
+"""
+
+import structlog
+
+from src.db.base import get_db_context
+from src.models.knowledge import (
+    CategoryCount,
+    EntryStatus,
+    EntryType,
+    KnowledgeEntry,
+    KnowledgeEntryCreate,
+    KnowledgeEntryUpdate,
+    KnowledgeListResponse,
+)
+from src.repositories.knowledge_repository import KnowledgeDBRepository
+
+logger = structlog.get_logger(__name__)
+
+# =============================================================================
+# Singleton
+# =============================================================================
+
+_knowledge_service: "KnowledgeService | None" = None
+
+
+def get_knowledge_service() -> "KnowledgeService":
+    """取得 Knowledge Service 實例"""
+    global _knowledge_service
+    if _knowledge_service is None:
+        _knowledge_service = KnowledgeService()
+    return _knowledge_service
+
+
+class KnowledgeService:
+    """Knowledge Base 業務邏輯"""
+
+    async def create_entry(self, data: KnowledgeEntryCreate) -> KnowledgeEntry:
+        """建立知識條目"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            entry = await repo.create(data)
+            logger.info(
+                "knowledge_entry_created",
+                entry_id=entry.id,
+                entry_type=entry.entry_type,
+                source=entry.source,
+            )
+            return entry
+
+    async def get_entry(self, entry_id: str) -> KnowledgeEntry | None:
+        """取得知識條目 (view_count +1)"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            entry = await repo.get_by_id(entry_id)
+            if entry:
+                await repo.increment_view_count(entry_id)
+                entry.view_count += 1
+            return entry
+
+    async def update_entry(
+        self, entry_id: str, data: KnowledgeEntryUpdate
+    ) -> KnowledgeEntry | None:
+        """更新知識條目"""
+        update_data = data.model_dump(exclude_none=True)
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            if not update_data:
+                return await repo.get_by_id(entry_id)
+            return await repo.update(entry_id, update_data)
+
+    async def approve_entry(self, entry_id: str) -> KnowledgeEntry | None:
+        """審核通過 (draft/review → approved)"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            entry = await repo.get_by_id(entry_id)
+            if not entry:
+                return None
+            if entry.status == EntryStatus.APPROVED:
+                return entry
+            return await repo.update(entry_id, {"status": EntryStatus.APPROVED})
+
+    async def archive_entry(self, entry_id: str) -> bool:
+        """封存 (軟刪除)"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            return await repo.delete(entry_id)
+
+    async def list_entries(
+        self,
+        category: str | None = None,
+        entry_type: EntryType | None = None,
+        status: EntryStatus | None = None,
+        tags: list[str] | None = None,
+        q: str | None = None,
+        limit: int = 20,
+        offset: int = 0,
+    ) -> KnowledgeListResponse:
+        """列出知識條目 + 分類統計"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            items, total = await repo.list_entries(
+                category=category,
+                entry_type=entry_type,
+                status=status,
+                tags=tags,
+                q=q,
+                limit=limit,
+                offset=offset,
+            )
+            categories_raw = await repo.get_categories()
+            categories = [
+                CategoryCount(category=cat, count=cnt) for cat, cnt in categories_raw
+            ]
+            return KnowledgeListResponse(
+                items=items, total=total, categories=categories
+            )
+
+    async def search(self, query: str, limit: int = 20) -> list[KnowledgeEntry]:
+        """關鍵字搜尋"""
+        async with get_db_context() as db:
+            repo = KnowledgeDBRepository(db)
+            return await repo.search(query, limit)