fix: redirect to /setup/unresolved after series scan completes

- Add 'system_progress' event type to loading page redirect condition
- Add checkUnresolvedAndRedirect() for phase=initial to handle race condition
  where backend initialization completes before WebSocket connects
- Backend now emits series_sync progress events during initial setup
- Loading page checks /api/setup/unresolved immediately on load for phase=initial
- Fixes users getting stuck on loading page after setup

src/server/services/initialization_service.py

@@ -271,7 +271,7 @@ async def _load_series_into_memory(progress_service=None) -> None:
         )
 
 
-async def _scan_folders_to_database(progress_service=None) -> int:
+async def _scan_folders_to_database(progress_service=None) -> tuple[int, int]:
     """Scan anime folders and create AnimeSeries DB records.
 
     This function runs during initial setup only. It delegates to
@@ -285,7 +285,7 @@ async def _scan_folders_to_database(progress_service=None) -> int:
         progress_service: Optional ProgressService for progress updates
 
     Returns:
-        int: Number of new series created
+        Tuple of (number of new series created, number of unresolved folders)
     """
     logger.info("Scanning anime folders for new series...")
 
@@ -293,16 +293,17 @@ async def _scan_folders_to_database(progress_service=None) -> int:
         logger.info(
             "Anime directory not configured or does not exist, skipping folder scan"
         )
-        return 0
+        return 0, 0
 
     # Use SetupService to handle the scanning and creation
-    created_count = await SetupService.run()
+    created_count, unresolved_count = await SetupService.run()
 
     logger.info(
         "Folder scan complete",
-        created=created_count
+        created=created_count,
+        unresolved=unresolved_count
     )
-    return created_count
+    return created_count, unresolved_count
 
 
 async def _validate_anime_directory(progress_service=None) -> bool:
@@ -380,7 +381,7 @@ async def perform_initial_setup(progress_service=None):
     # Perform the actual initialization
     try:
         # Scan folders and create AnimeSeries records first
-        folder_scan_count = await _scan_folders_to_database(progress_service)
+        folder_scan_count, unresolved_count = await _scan_folders_to_database(progress_service)
         if folder_scan_count > 0:
             logger.info("Created %d series from anime folders", folder_scan_count)
 
@@ -398,11 +399,20 @@ async def perform_initial_setup(progress_service=None):
         await _mark_initial_scan_completed()
 
         # Mark loading as complete in config (used by middleware to allow redirect to /login)
+        # Only mark complete if there are no unresolved folders - otherwise user needs
+        # to resolve them first via /setup/unresolved
         try:
             from src.server.services.config_service import get_config_service
             config_svc = get_config_service()
             init_config = config_svc.load_config()
-            init_config.other['loading_complete'] = True
+            if unresolved_count == 0:
+                init_config.other['loading_complete'] = True
+                logger.info("No unresolved folders - marking loading complete")
+            else:
+                logger.info(
+                    "Unresolved folders exist (%d) - deferring loading_complete",
+                    unresolved_count
+                )
             config_svc.save_config(init_config, create_backup=False)
         except Exception as e:
             logger.warning("Failed to save loading_complete flag: %s", e)