feat: Add quota check decorator and implement tenant-level API rate limiting

- Add quota check decorator module quota_stub.py, providing community edition stub implementation
- Add quota check decorators to multiple controllers
- Implement tenant-level API call rate limiting
- Remove redundant plan fields from tenant_model.py
- Optimize user permission check logic with added error handling

api/app/core/quota_stub.py

@@ -0,0 +1,44 @@
+"""
+配额检查 stub - 社区版使用，所有检查直接放行。
+企业版通过 premium.platform_admin.quota_decorator 提供真实实现。
+"""
+from functools import wraps
+from typing import Callable
+
+
+def _noop_decorator(func: Callable) -> Callable:
+    """空装饰器，直接放行"""
+    return func
+
+
+def _noop_check(*args, **kwargs):
+    """空检查函数，直接放行"""
+    pass
+
+
+try:
+    from premium.platform_admin.quota_decorator import (
+        check_workspace_quota,
+        check_skill_quota,
+        check_app_quota,
+        check_knowledge_capacity_quota,
+        check_memory_engine_quota,
+        check_end_user_quota,
+        check_ontology_project_quota,
+        check_model_quota,
+        check_model_activation_quota,
+        get_quota_usage,
+        _check_quota,
+    )
+except ModuleNotFoundError:
+    check_workspace_quota = _noop_decorator
+    check_skill_quota = _noop_decorator
+    check_app_quota = _noop_decorator
+    check_knowledge_capacity_quota = _noop_decorator
+    check_memory_engine_quota = _noop_decorator
+    check_end_user_quota = _noop_decorator
+    check_ontology_project_quota = _noop_decorator
+    check_model_quota = _noop_decorator
+    check_model_activation_quota = _noop_decorator
+    get_quota_usage = lambda db, tenant_id: {}
+    _check_quota = _noop_check