feat(aiot): 告警三表结构升级 + 腾讯云COS对象存储集成

1. 新增三表结构: alarm_event(主表), alarm_event_ext(算法扩展), alarm_llm_analysis(大模型分析)
2. 新增 AlarmEventService 服务，支持 MQTT/HTTP 双路创建告警
3. MQTT handler 双写新旧表，平滑过渡
4. 重写 yudao_aiot_alarm 路由，对接新告警服务
5. 集成腾讯云 COS 对象存储：上传、预签名URL、STS临时凭证
6. 新增 storage 路由：upload/presign/upload-url/sts 四个接口
7. COS 未启用时自动降级本地 uploads/ 目录存储
8. 新增数据迁移脚本 migrate_to_alarm_event.py
9. 删除根目录 main.py（非项目入口）

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/config.py

@@ -15,13 +15,16 @@ class DatabaseConfig:
 
 
 @dataclass
-class OSSConfig:
-    """OSS 存储配置"""
-    access_key_id: str = ""
-    access_key_secret: str = ""
-    endpoint: str = "oss-cn-hangzhou.aliyuncs.com"
-    bucket_name: str = ""
-    url_prefix: str = ""
+class COSConfig:
+    """腾讯云 COS 存储配置"""
+    secret_id: str = ""
+    secret_key: str = ""
+    region: str = "ap-beijing"
+    bucket: str = ""                   # 格式: bucketname-appid
+    upload_prefix: str = "alerts"      # 对象 Key 前缀
+    presign_expire: int = 1800         # 预签名URL有效期（秒），默认30分钟
+    sts_expire: int = 1800             # STS 临时凭证有效期（秒）
+    enabled: bool = False              # 是否启用 COS（False 时使用本地存储）
 
 
 @dataclass
@@ -57,7 +60,7 @@ class MQTTConfig:
 class Settings(BaseModel):
     """全局配置"""
     database: DatabaseConfig = DatabaseConfig()
-    oss: OSSConfig = OSSConfig()
+    cos: COSConfig = COSConfig()
     app: AppConfig = AppConfig()
     ai_model: AIModelConfig = AIModelConfig()
     mqtt: MQTTConfig = MQTTConfig()
@@ -72,12 +75,15 @@ def load_settings() -> Settings:
         database=DatabaseConfig(
             url=os.getenv("DATABASE_URL", "sqlite:///./data/alert_platform.db"),
         ),
-        oss=OSSConfig(
-            access_key_id=os.getenv("OSS_ACCESS_KEY_ID", ""),
-            access_key_secret=os.getenv("OSS_ACCESS_KEY_SECRET", ""),
-            endpoint=os.getenv("OSS_ENDPOINT", "oss-cn-hangzhou.aliyuncs.com"),
-            bucket_name=os.getenv("OSS_BUCKET_NAME", ""),
-            url_prefix=os.getenv("OSS_URL_PREFIX", ""),
+        cos=COSConfig(
+            secret_id=os.getenv("COS_SECRET_ID", ""),
+            secret_key=os.getenv("COS_SECRET_KEY", ""),
+            region=os.getenv("COS_REGION", "ap-beijing"),
+            bucket=os.getenv("COS_BUCKET", ""),
+            upload_prefix=os.getenv("COS_UPLOAD_PREFIX", "alerts"),
+            presign_expire=int(os.getenv("COS_PRESIGN_EXPIRE", "1800")),
+            sts_expire=int(os.getenv("COS_STS_EXPIRE", "1800")),
+            enabled=os.getenv("COS_ENABLED", "false").lower() == "true",
         ),
         app=AppConfig(
             host=os.getenv("APP_HOST", "0.0.0.0"),