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/db/models.py

@@ -30,6 +30,7 @@ from sqlalchemy.orm import Mapped, mapped_column
 from src.db.base import Base
 from src.models.approval import ApprovalStatus, RiskLevel
 from src.models.incident import IncidentStatus, Severity
+from src.models.knowledge import EntrySource, EntryStatus, EntryType
 
 # =============================================================================
 # Helper Functions
@@ -454,3 +455,100 @@ class IncidentRecord(Base):
         Index("ix_incident_created_at", "created_at"),
         Index("ix_incident_resolved_at", "resolved_at"),
     )
+
+
+# =============================================================================
+# KnowledgeEntry - Knowledge Base Phase 1
+# =============================================================================
+
+class KnowledgeEntryRecord(Base):
+    """
+    知識庫條目 - Knowledge Base Phase 1
+
+    兩層架構:
+    - KnowledgeEntry: 知識條目 (此表)
+    - Playbook: 獨立 Redis，透過 related_playbook_id 關聯
+
+    建立時間: 2026-04-02 (台北時區)
+    建立者: Claude Code (Knowledge Base Phase 1)
+    """
+    __tablename__ = "knowledge_entries"
+
+    # Primary Key
+    id: Mapped[str] = mapped_column(
+        String(36),
+        primary_key=True,
+        default=generate_uuid,
+    )
+
+    # Core Fields
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    content: Mapped[str] = mapped_column(Text, nullable=False)
+    entry_type: Mapped[str] = mapped_column(
+        SQLEnum(EntryType),
+        nullable=False,
+        comment="incident_case / runbook / best_practice / postmortem",
+    )
+    category: Mapped[str] = mapped_column(
+        String(100),
+        nullable=False,
+        comment="分類樹節點 (基礎設施/應用層/AI系統/安全合規)",
+    )
+    tags: Mapped[list[dict[str, Any]]] = mapped_column(
+        JSON,
+        default=list,
+        nullable=False,
+        comment="標籤列表 (JSONB)",
+    )
+
+    # Source & Status
+    source: Mapped[str] = mapped_column(
+        SQLEnum(EntrySource),
+        nullable=False,
+        comment="ai_extracted / human",
+    )
+    status: Mapped[str] = mapped_column(
+        SQLEnum(EntryStatus),
+        default=EntryStatus.DRAFT,
+        nullable=False,
+        comment="draft / review / approved / archived",
+    )
+
+    # Relations (soft references, not FK)
+    related_incident_id: Mapped[str | None] = mapped_column(
+        String(30),
+        nullable=True,
+        comment="關聯 Incident ID",
+    )
+    related_playbook_id: Mapped[str | None] = mapped_column(
+        String(255),
+        nullable=True,
+        comment="關聯 Playbook Redis Key",
+    )
+
+    # Metrics
+    view_count: Mapped[int] = mapped_column(
+        Integer,
+        default=0,
+        nullable=False,
+    )
+
+    # Metadata
+    created_by: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=utc_now,
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=utc_now,
+        onupdate=utc_now,
+    )
+
+    # Indexes
+    __table_args__ = (
+        Index("ix_knowledge_entry_type", "entry_type"),
+        Index("ix_knowledge_category", "category"),
+        Index("ix_knowledge_status", "status"),
+        Index("ix_knowledge_created_at", "created_at"),
+    )