chore: 整合 migration 文件并优化配置

- 整合 18 个分散的 migration 文件为 5 个模块化文件
- settings.py 支持 .env.local 覆盖 .env
- 移除 user schema 中未使用的 country 字段正则
- 更新 profile protocol 文档移除 country 字段
- pyproject.toml 添加 ruff 到 dev 依赖
- 简化 integration test conftest 邮箱 fixture

backend/src/core/config/settings.py

@@ -240,13 +240,18 @@ class AppleIapSettings(BaseModel):
     server_notifications_url: str | None = None
 
 
-def _resolve_env_file() -> str:
+def _resolve_env_files() -> list[str]:
+    """Resolve env files in order: .env.local overrides .env"""
     current = Path(__file__).resolve()
     for parent in [current, *current.parents]:
-        candidate = parent / ".env"
-        if candidate.is_file():
-            return str(candidate)
-    return ".env"
+        env_file = parent / ".env"
+        if env_file.is_file():
+            files = [str(env_file)]
+            env_local = parent / ".env.local"
+            if env_local.is_file():
+                files.append(str(env_local))
+            return files
+    return [".env"]
 
 
 PROJECT_ROOT = _resolve_project_root()
@@ -305,7 +310,7 @@ class Settings(BaseSettings):
         return self.taskiq.result_backend_url or self.redis.url
 
     model_config: ClassVar[SettingsConfigDict] = SettingsConfigDict(
-        env_file=_resolve_env_file(),
+        env_file=_resolve_env_files(),
         env_prefix="ERYAO_",
         env_nested_delimiter="__",
         case_sensitive=False,