perf: 拆分热力图为独立接口并添加 Redis 缓存

- 新增独立热力图 API 端点 (/api/admin/usage/heatmap, /api/users/me/usage/heatmap)
- 添加 Redis 缓存层 (5分钟 TTL)，减少数据库查询
- 用户角色变更时清除热力图缓存
- 前端并行加载统计数据和热力图，添加加载/错误状态显示
- 修复 cache_decorator 缺少 JSON 解析错误处理的问题
- 更新 docker-compose 启动命令提示

src/api/admin/usage/routes.py

@@ -73,6 +73,20 @@ async def get_usage_stats(
     return await pipeline.run(adapter=adapter, http_request=request, db=db, mode=adapter.mode)
 
 
+@router.get("/heatmap")
+async def get_activity_heatmap(
+    request: Request,
+    db: Session = Depends(get_db),
+):
+    """
+    Get activity heatmap data for the past 365 days.
+
+    This endpoint is cached for 5 minutes to reduce database load.
+    """
+    adapter = AdminActivityHeatmapAdapter()
+    return await pipeline.run(adapter=adapter, http_request=request, db=db, mode=adapter.mode)
+
+
 @router.get("/records")
 async def get_usage_records(
     request: Request,
@@ -168,12 +182,6 @@ class AdminUsageStatsAdapter(AdminApiAdapter):
             (Usage.status_code >= 400) | (Usage.error_message.isnot(None))
         ).count()
 
-        activity_heatmap = UsageService.get_daily_activity(
-            db=db,
-            window_days=365,
-            include_actual_cost=True,
-        )
-
         context.add_audit_metadata(
             action="usage_stats",
             start_date=self.start_date.isoformat() if self.start_date else None,
@@ -204,10 +212,22 @@ class AdminUsageStatsAdapter(AdminApiAdapter):
                 ),
                 "cache_read_cost": float(cache_stats.cache_read_cost or 0) if cache_stats else 0,
             },
-            "activity_heatmap": activity_heatmap,
         }
 
 
+class AdminActivityHeatmapAdapter(AdminApiAdapter):
+    """Activity heatmap adapter with Redis caching."""
+
+    async def handle(self, context):  # type: ignore[override]
+        result = await UsageService.get_cached_heatmap(
+            db=context.db,
+            user_id=None,
+            include_actual_cost=True,
+        )
+        context.add_audit_metadata(action="activity_heatmap")
+        return result
+
+
 class AdminUsageByModelAdapter(AdminApiAdapter):
     def __init__(self, start_date: Optional[datetime], end_date: Optional[datetime], limit: int):
         self.start_date = start_date