refactor(api): Phase 17 metrics.py Router 層違規修復

移除 Router 層直接 DB 存取，遵循 leWOOOgo 積木化原則：
- 新增 IMetricsRepository Protocol (interfaces.py)
- 新增 MetricsDBRepository 封裝 DB 查詢
- 新增 MetricsService 封裝業務邏輯
- Router 層只做 HTTP 轉發

架構: Router → Service → Repository → PostgreSQL

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/repositories/__init__.py

@@ -24,18 +24,26 @@ from src.repositories.incident_repository import (
 from src.repositories.interfaces import (
     IApprovalRepository,
     IIncidentRepository,
+    IMetricsRepository,
     ITimelineRepository,
 )
+from src.repositories.metrics_repository import (
+    MetricsDBRepository,
+    get_metrics_repository,
+)
 
 __all__ = [
     # Interfaces
     "IApprovalRepository",
     "IIncidentRepository",
+    "IMetricsRepository",
     "ITimelineRepository",
     # Implementations
     "ApprovalDBRepository",
     "IncidentDBRepository",
+    "MetricsDBRepository",
     # Getters
     "get_approval_repository",
     "get_incident_repository",
+    "get_metrics_repository",
 ]

apps/api/src/repositories/interfaces.py

@@ -125,3 +125,49 @@ class ITimelineRepository(Protocol):
     ) -> list[dict]:
         """取得最近的 Timeline 事件"""
         ...
+
+
+@runtime_checkable
+class IMetricsRepository(Protocol):
+    """
+    Metrics Repository Protocol
+
+    職責: Metrics 相關 DB 查詢 (AI Success Rate)
+    實作: MetricsDBRepository (PostgreSQL)
+
+    版本: v1.0
+    建立: 2026-03-26 (台北時區)
+    建立者: Claude Code (Phase 17 技術債修復)
+    """
+
+    async def get_ai_success_rate(
+        self,
+        hours: int = 24,
+    ) -> tuple[float, int, int]:
+        """
+        計算 AI 提案成功執行率
+
+        Args:
+            hours: 統計時間範圍 (小時)
+
+        Returns:
+            (success_rate_percent, executed_count, total_count)
+        """
+        ...
+
+    async def get_ai_success_trend(
+        self,
+        hours: int = 24,
+        points: int = 10,
+    ) -> list[float]:
+        """
+        取得 AI 成功率趨勢 (Sparkline 用)
+
+        Args:
+            hours: 統計時間範圍 (小時)
+            points: 趨勢點數量
+
+        Returns:
+            list[float]: 每小時成功率列表 (由舊到新)
+        """
+        ...

apps/api/src/repositories/metrics_repository.py

@@ -0,0 +1,186 @@
+"""
+Metrics Repository - PostgreSQL 實作
+=====================================
+Phase 17 技術債修復: Router 層違規抽取
+
+職責: Metrics 相關 DB 查詢 (AI Success Rate 統計)
+設計: 實作 IMetricsRepository Protocol
+
+版本: v1.0
+建立: 2026-03-26 (台北時區)
+建立者: Claude Code (Phase 17 技術債修復)
+"""
+
+from datetime import UTC, datetime, timedelta
+
+import structlog
+from sqlalchemy import text
+
+from src.db.base import get_db_context
+from src.repositories.interfaces import IMetricsRepository
+
+logger = structlog.get_logger(__name__)
+
+
+# =============================================================================
+# MetricsDBRepository
+# =============================================================================
+
+
+class MetricsDBRepository(IMetricsRepository):
+    """
+    Metrics Repository - PostgreSQL 實作
+
+    職責:
+    - AI Success Rate 統計查詢
+    - 趨勢數據查詢 (Sparkline)
+
+    純 CRUD 操作，不含業務邏輯
+    業務邏輯請放在 Service 層
+    """
+
+    async def get_ai_success_rate(
+        self,
+        hours: int = 24,
+    ) -> tuple[float, int, int]:
+        """
+        計算 AI 提案成功執行率
+
+        統帥鐵律: 若無數據，回傳真實的 0，嚴禁造假
+
+        Args:
+            hours: 統計時間範圍 (小時)
+
+        Returns:
+            (success_rate_percent, executed_count, total_count)
+        """
+        try:
+            async with get_db_context() as session:
+                cutoff = datetime.now(UTC) - timedelta(hours=hours)
+                cutoff_str = cutoff.isoformat()
+
+                # Query: 統計 executed vs total (approved + executed + execution_failed)
+                query = text("""
+                    SELECT
+                        COUNT(CASE WHEN status = 'executed' THEN 1 END) as executed_count,
+                        COUNT(*) as total_count
+                    FROM approval_records
+                    WHERE created_at >= :cutoff
+                    AND status IN ('approved', 'executed', 'execution_failed')
+                """)
+
+                result = await session.execute(query, {"cutoff": cutoff_str})
+                row = result.fetchone()
+
+                if row and row.total_count > 0:
+                    executed = row.executed_count or 0
+                    total = row.total_count
+                    success_rate = (executed / total) * 100
+                else:
+                    executed = 0
+                    total = 0
+                    success_rate = 0.0
+
+                logger.debug(
+                    "ai_success_rate_queried",
+                    hours=hours,
+                    executed=executed,
+                    total=total,
+                    rate=success_rate,
+                )
+
+                return success_rate, executed, total
+
+        except Exception as e:
+            logger.exception(
+                "ai_success_rate_query_error",
+                hours=hours,
+                error=str(e),
+            )
+            # 統帥鐵律: 發生錯誤時回傳真實的 0，非假數據
+            return 0.0, 0, 0
+
+    async def get_ai_success_trend(
+        self,
+        hours: int = 24,
+        points: int = 10,
+    ) -> list[float]:
+        """
+        取得 AI 成功率趨勢 (Sparkline 用)
+
+        統帥鐵律: 若無數據，回傳真實的 [0.0] * points，嚴禁造假
+
+        Args:
+            hours: 統計時間範圍 (小時)
+            points: 趨勢點數量
+
+        Returns:
+            list[float]: 每小時成功率列表 (由舊到新)
+        """
+        try:
+            async with get_db_context() as session:
+                cutoff = datetime.now(UTC) - timedelta(hours=hours)
+                cutoff_str = cutoff.isoformat()
+
+                # Trend: 過去 N 個時間點的成功率 (每小時一點)
+                trend_query = text("""
+                    SELECT
+                        strftime('%Y-%m-%d %H:00:00', created_at) as hour_bucket,
+                        COUNT(CASE WHEN status = 'executed' THEN 1 END) * 100.0 /
+                        NULLIF(COUNT(*), 0) as hourly_rate
+                    FROM approval_records
+                    WHERE created_at >= :cutoff
+                    AND status IN ('approved', 'executed', 'execution_failed')
+                    GROUP BY hour_bucket
+                    ORDER BY hour_bucket DESC
+                    LIMIT :limit
+                """)
+
+                result = await session.execute(
+                    trend_query,
+                    {"cutoff": cutoff_str, "limit": points},
+                )
+                rows = result.fetchall()
+
+                if rows:
+                    # 由舊到新排列
+                    trend_values = [float(r.hourly_rate or 0) for r in reversed(rows)]
+                    # 如果點數不足，前面補 0
+                    if len(trend_values) < points:
+                        trend_values = [0.0] * (points - len(trend_values)) + trend_values
+                else:
+                    trend_values = [0.0] * points
+
+                logger.debug(
+                    "ai_success_trend_queried",
+                    hours=hours,
+                    points=points,
+                    actual_points=len(trend_values),
+                )
+
+                return trend_values
+
+        except Exception as e:
+            logger.exception(
+                "ai_success_trend_query_error",
+                hours=hours,
+                points=points,
+                error=str(e),
+            )
+            # 統帥鐵律: 發生錯誤時回傳真實的 0，非假數據
+            return [0.0] * points
+
+
+# =============================================================================
+# Singleton
+# =============================================================================
+
+_metrics_repository: MetricsDBRepository | None = None
+
+
+def get_metrics_repository() -> MetricsDBRepository:
+    """取得 MetricsDBRepository 實例 (Singleton)"""
+    global _metrics_repository
+    if _metrics_repository is None:
+        _metrics_repository = MetricsDBRepository()
+    return _metrics_repository