fix(middleware): prevent premature redirect to /login during loading

Users were incorrectly redirected to /login during the initial loading phase
before the loading was actually complete. Added loading_started and
loading_complete flags to properly track the initialization state so
the setup redirect middleware knows when it's safe to redirect.

src/server/middleware/setup_redirect.py

@@ -118,6 +118,20 @@ class SetupRedirectMiddleware(BaseHTTPMiddleware):
             return bool(other.get('unresolved_completed', False))
         except Exception:
             return False
+
+    def _is_loading_complete(self) -> bool:
+        """Check if initial loading has completed.
+        
+        Returns:
+            True if loading is complete, False otherwise
+        """
+        try:
+            config_service = get_config_service()
+            config = config_service.load_config()
+            other = config.other or {}
+            return bool(other.get('loading_complete', False))
+        except Exception:
+            return False
     
     async def dispatch(
         self, request: Request, call_next: Callable
@@ -149,14 +163,17 @@ class SetupRedirectMiddleware(BaseHTTPMiddleware):
                     # Handle phase query parameter
                     phase = query_params.get("phase")
                     if phase == "initial":
-                        # phase=initial should not be accessed after setup is complete
-                        # Redirect to login
-                        return RedirectResponse(url="/login", status_code=302)
+                        # Only redirect if loading has actually completed
+                        # If loading_started=True but loading_complete=False, user should stay
+                        # on loading page to see progress
+                        if self._is_loading_complete():
+                            return RedirectResponse(url="/login", status_code=302)
+                        # Otherwise, allow access to loading page (loading in progress)
                     elif not phase:
-                        # No phase specified and setup is complete
-                        # Redirect to login since user should be further in the flow
-                        return RedirectResponse(url="/login", status_code=302)
-                    # phase=nfo is allowed - it triggers the NFO scan phase
+                        # No phase specified and loading is complete
+                        if self._is_loading_complete():
+                            return RedirectResponse(url="/login", status_code=302)
+                    # phase=nfo is always allowed - it triggers the NFO scan phase
         
         # Skip setup check for exempt paths
         if self._is_path_exempt(path):