refactor: P7 切尾——删除 application/extensions/utils，WSGI 切 src

【切尾】
- src/app.py：应用工厂（原 application/factory.py）
- src/extensions.py：扩展注册编排（原 extensions/）
- src/wsgi.py：生产 WSGI 入口
- 根 app.py 改为 from src.app import create_app（开发入口保留）
- gunicorn/Docker/compose 指向 src.wsgi:app
- 删除 application/、extensions/、utils/（全部代码已迁入 src/）

【清理】21 个 router 中间件导入改 src.core；修复 level 服务潜在 bug
（utils.load2dict 不存在 → model_to_dict）；测试文件 R 导入改 src.core

【里程碑】全项目 flake8 从 P1 基线 154 条 → **0 条**；
12 passed；app.py 与 src.wsgi 双入口均启动

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

config/__init__.py

@@ -33,7 +33,8 @@ _load_env_file()
 # ============================================================
 
 # 应用基础配置
-from config.app import (
+from config.app import (  # noqa: E402
+
     FLASK_NAME, FLASK_VERSION, FLASK_SECRET_KEY, FLASK_HOST, FLASK_PORT,
     FLASK_SITE_DOMAIN, FLASK_APP, FLASK_ENV, FLASK_DEBUG, FLASK_USE_RELOADER,
     FLASK_DEMO, FLASK_SYSTEM, FLASK_ROOT_PATH, FLASK_TEMPLATE_FOLDER,
@@ -42,19 +43,22 @@ from config.app import (
 )
 
 # 数据库配置
-from config.database import (
+from config.database import (  # noqa: E402
+
     DatabaseConfig, DB_PREFIX, DB_DRIVER, DB_HOST, DB_PORT, DB_DATABASE,
     DB_USERNAME, DB_PASSWORD, DB_DEBUG, DB_SSL, DATABASE_URL,
 )
 
 # Redis 缓存配置
-from config.redis import (
+from config.redis import (  # noqa: E402
+
     REDIS_HOST, REDIS_PORT, REDIS_PASSWORD, REDIS_INDEX,
     REDIS_AUTH, REDIS_DECODE_RESPONSES, REDIS_URL,
 )
 
 # JWT + 权限 + 白名单配置
-from config.auth import (
+from config.auth import (  # noqa: E402
+
     JWT_SALT, JWT_EXPIRE_MINUTES, LOGIN_FAIL_MAX, LOGIN_LOCK_SECONDS,
     PERMISSION_ENABLED, INTERNAL_API_KEY,
     INTERNAL_ALLOWED_IPS, LOGIN_WHITELIST_EXACT, LOGIN_WHITELIST_PREFIX,
@@ -63,21 +67,24 @@ from config.auth import (
 )
 
 # 邮件配置
-from config.mail import (
+from config.mail import (  # noqa: E402
+
     MAIL_MAILER, MAIL_SERVER, MAIL_PORT, MAIL_USE_SSL,
     MAIL_USERNAME, MAIL_PASSWORD, MAIL_ENCRYPTION,
     MAIL_FROM_NAME, MAIL_FROM_ADDRESS,
 )
 
 # 短信配置
-from config.sms import (
+from config.sms import (  # noqa: E402
+
     SMS_PROVIDER, SMS_ALIYUN_ACCESS_KEY_ID, SMS_ALIYUN_ACCESS_KEY_SECRET,
     SMS_ALIYUN_SIGN_NAME, SMS_ALIYUN_ENDPOINT,
     SMS_ALIYUN_CONNECT_TIMEOUT, SMS_ALIYUN_READ_TIMEOUT,
 )
 
 # 验证码配置
-from config.captcha import (
+from config.captcha import (  # noqa: E402
+
     CAPTCHA_LENGTH,
     CAPTCHA_EXPIRE,
     CAPTCHA_RATE_LIMIT,