feat(api): 統一使用台北時區 UTC+8 (禁止 UTC)

- 新增 src/utils/timezone.py 時區工具函式
- 修改 11 個後端檔案，全部改用 now_taipei()
- 更新 HARD_RULES.md 加入時區鐵律章節
- 更新 Skills 02/04 加入時區禁令

🔴 HARD RULE: 禁止 datetime.utcnow() / datetime.now(UTC)
✅ 正確做法: from src.utils.timezone import now_taipei

Memory: feedback_timezone_taipei.md

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

apps/api/src/services/executor.py

@@ -21,7 +21,7 @@ Supported Operations:
 import asyncio
 import time
 from dataclasses import dataclass
-from datetime import UTC, datetime
+from src.utils.timezone import now_taipei, now_taipei_iso
 from enum import Enum
 from pathlib import Path
 from typing import Any
@@ -376,7 +376,7 @@ class ActionExecutor:
                     "template": {
                         "metadata": {
                             "annotations": {
-                                "kubectl.kubernetes.io/restartedAt": datetime.now(UTC).isoformat()
+                                "kubectl.kubernetes.io/restartedAt": now_taipei().isoformat()
                             }
                         }
                     }
@@ -1060,7 +1060,7 @@ async def execute_approved_proposal(approval_id: str) -> ExecutionResult:
     # Step 5: 更新狀態
     new_status = "executed" if result.success else "failed"
     execution_log = {
-        "executed_at": datetime.now(UTC).isoformat(),
+        "executed_at": now_taipei().isoformat(),
         "success": result.success,
         "stdout": result.k8s_response.get("stdout", "") if result.k8s_response else "",
         "stderr": result.error or "",