fix: convert RBAC_FILE constant to getter function to fix CI test failures

dashboard/backend/rbac.py

@@ -8,7 +8,9 @@ from fastapi import HTTPException, Request, status, Depends
 
 import config
 
-RBAC_FILE = os.path.join(config.VOLUME_ROOT, "docker/nas-dashboard/rbac.json")
+def get_rbac_file():
+    return os.path.join(config.VOLUME_ROOT, "docker/nas-dashboard/rbac.json")
+
 _rbac_lock = threading.RLock()
 
 ROLE_GROUP_MAP = {
@@ -38,8 +40,9 @@ class User(BaseModel):
 
 def load_rbac() -> dict:
     try:
-        if os.path.exists(RBAC_FILE):
+        rbac_path = get_rbac_file()
-            with open(RBAC_FILE) as f:
+        if os.path.exists(rbac_path):
+            with open(rbac_path) as f:
                 return json.load(f)
     except Exception:
         pass
@@ -64,12 +67,12 @@ def update_rbac(mutator):
     with _rbac_lock:
         data = load_rbac()
         result = mutator(data)
-        _atomic_json_write(RBAC_FILE, data)
+        _atomic_json_write(get_rbac_file(), data)
         return result
 
 
 def save_rbac(data: dict):
-    _atomic_json_write(RBAC_FILE, data)
+    _atomic_json_write(get_rbac_file(), data)
 
 
 def resolve_role(groups: list[str]) -> Optional[str]: