feat: integrate NFO repair into scheduled folder scan

- Add FolderScanService.run_folder_scan() calling perform_nfo_repair_scan()
- Remove startup-time NFO repair from fastapi_app lifespan
- Update docs/NFO_GUIDE.md: repair now runs as part of daily scan
- Update tests to verify integration wiring
- Update ARCHITECTURE.md and scheduler_service for scan scheduling

src/server/fastapi_app.py

@@ -242,7 +242,6 @@ async def lifespan(_application: FastAPI):
         from src.server.services.initialization_service import (
             perform_initial_setup,
             perform_media_scan_if_needed,
-            perform_nfo_repair_scan,
             perform_nfo_scan_if_needed,
         )
         
@@ -313,10 +312,6 @@ async def lifespan(_application: FastAPI):
 
                 # Run media scan only on first run
                 await perform_media_scan_if_needed(background_loader)
-
-                # Scan every series NFO on startup and repair any that are
-                # missing required tags by queuing them for background reload
-                await perform_nfo_repair_scan(background_loader)
             else:
                 logger.info(
                     "Download service initialization skipped - "

src/server/services/folder_scan_service.py

@@ -0,0 +1,85 @@
+"""Folder scan service for daily maintenance tasks.
+
+Encapsulates the daily folder-scan logic (orphaned-file detection,
+metadata refresh, and missing-episode queuing) so that the scheduler
+remains clean and the scan can be tested independently.
+"""
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+from typing import Optional
+
+import structlog
+
+from src.server.services.initialization_service import perform_nfo_repair_scan
+
+logger = structlog.get_logger(__name__)
+
+# Module-level semaphore to limit concurrent TMDB operations to 3.
+_TMDB_SEMAPHORE: asyncio.Semaphore = asyncio.Semaphore(3)
+
+
+class FolderScanServiceError(Exception):
+    """Service-level exception for folder-scan operations."""
+
+
+class FolderScanService:
+    """Performs daily maintenance scans over the anime library folder.
+
+    The service is intentionally stateless; a new instance can be created
+    for every scheduled invocation or test case.
+    """
+
+    async def run_folder_scan(self) -> None:
+        """Execute the daily folder scan.
+
+        Checks prerequisites, logs progress, and delegates to sub-task
+        helpers.  Any unhandled exception is caught and logged so the
+        scheduler task never crashes.
+        """
+        logger.info("Folder scan started")
+
+        try:
+            if not self._prerequisites_met():
+                return
+
+            # 1.3 — Repair incomplete NFO files in the background.
+            logger.info("Starting NFO repair scan as part of folder scan")
+            await perform_nfo_repair_scan(background_loader=None)
+            logger.info("NFO repair scan queued; repairs will continue in background")
+
+            # Sub-tasks 1.4–1.5 will fill in the actual work here.
+            logger.info("Folder scan completed")
+        except Exception as exc:  # pylint: disable=broad-exception-caught
+            logger.error("Folder scan failed", error=str(exc), exc_info=True)
+
+    # ------------------------------------------------------------------
+    # Private helpers
+    # ------------------------------------------------------------------
+
+    def _prerequisites_met(self) -> bool:
+        """Verify that the environment is ready for a folder scan.
+
+        Returns:
+            True when ``settings.anime_directory`` exists and
+            ``settings.tmdb_api_key`` is configured.
+        """
+        from src.config.settings import settings  # noqa: PLC0415
+
+        if not settings.tmdb_api_key:
+            logger.warning("Folder scan skipped — TMDB API key not configured")
+            return False
+
+        if not settings.anime_directory:
+            logger.warning("Folder scan skipped — anime directory not configured")
+            return False
+
+        anime_dir = Path(settings.anime_directory)
+        if not anime_dir.is_dir():
+            logger.warning(
+                "Folder scan skipped — anime directory not found: %s", anime_dir
+            )
+            return False
+
+        return True

src/server/services/initialization_service.py

@@ -417,10 +417,10 @@ async def _repair_one_series(series_dir: Path, series_name: str) -> None:
 async def perform_nfo_repair_scan(background_loader=None) -> None:
     """Scan all series folders and repair incomplete tvshow.nfo files.
 
-    Runs on every application startup (not guarded by a run-once DB flag).
-    Checks each subfolder of ``settings.anime_directory`` for a ``tvshow.nfo``
-    and calls ``_repair_one_series`` for every file with absent or empty
-    required tags.
+    Called from ``FolderScanService.run_folder_scan()`` during the scheduled
+    daily folder scan (not on every startup).  Checks each subfolder of
+    ``settings.anime_directory`` for a ``tvshow.nfo`` and calls
+    ``_repair_one_series`` for every file with absent or empty required tags.
 
     Each repair task creates its own isolated :class:`NFOService` /
     :class:`TMDBClient` so concurrent tasks never share an ``aiohttp``

src/server/services/scheduler_service.py

@@ -356,6 +356,28 @@ class SchedulerService:
             else:
                 logger.debug("Auto-download after rescan is disabled — skipping")
 
+            # Folder scan (daily maintenance)
+            if self._config and self._config.folder_scan_enabled:
+                logger.info("Folder scan is enabled — starting")
+                try:
+                    from src.server.services.folder_scan_service import (  # noqa: PLC0415
+                        FolderScanService,
+                    )
+
+                    folder_scan_service = FolderScanService()
+                    await folder_scan_service.run_folder_scan()
+                except Exception as fs_exc:  # pylint: disable=broad-exception-caught
+                    logger.error(
+                        "Folder scan failed",
+                        error=str(fs_exc),
+                        exc_info=True,
+                    )
+                    await self._broadcast(
+                        "folder_scan_error", {"error": str(fs_exc)}
+                    )
+            else:
+                logger.debug("Folder scan is disabled — skipping")
+
         except Exception as exc:  # pylint: disable=broad-exception-caught
             logger.error("Scheduled rescan failed", error=str(exc), exc_info=True)
             await self._broadcast(