fix(scheduler): ensure scheduler starts after setup/config update

Add ensure_started() to SchedulerService as idempotent entry point.
Start scheduler in auth setup run_initialization() after NFO scan.
Sync anime_directory and start scheduler in config update endpoint.
Add unit and endpoint tests for ensure_started() behavior.

src/server/api/auth.py

@@ -163,6 +163,22 @@ async def setup_auth(req: SetupRequest):
                 # Perform NFO scan if configured
                 await perform_nfo_scan_if_needed(progress_service)
                 
+                # Start scheduler if anime_directory is now set
+                try:
+                    from src.server.services.scheduler_service import (
+                        get_scheduler_service,
+                    )
+
+                    scheduler_svc = get_scheduler_service()
+                    logger.info("Starting scheduler after initialization")
+                    await scheduler_svc.ensure_started()
+                    logger.info("Scheduler started successfully during setup")
+                except Exception as sched_exc:
+                    logger.warning(
+                        "Failed to start scheduler during setup: %s", sched_exc
+                    )
+                    # Continue — scheduler failure should not break initialization
+                
                 # Send completion event
                 from src.server.services.progress_service import ProgressType
                 await progress_service.start_progress(

src/server/api/config.py

@@ -1,7 +1,10 @@
+import logging
 from typing import Any, Dict, List, Optional
 
 from fastapi import APIRouter, Depends, HTTPException, status
 
+logger = logging.getLogger(__name__)
+
 from src.server.models.config import AppConfig, ConfigUpdate, ValidationResult
 from src.server.services.config_service import (
     ConfigBackupError,
@@ -28,16 +31,53 @@ def get_config(auth: Optional[dict] = Depends(require_auth)) -> AppConfig:
 
 
 @router.put("", response_model=AppConfig)
-def update_config(
+async def update_config(
     update: ConfigUpdate, auth: dict = Depends(require_auth)
 ) -> AppConfig:
     """Apply an update to the configuration and persist it.
 
-    Creates automatic backup before applying changes.
+    Creates automatic backup before applying changes. If anime_directory
+    is configured, starts the scheduler service.
     """
     try:
         config_service = get_config_service()
-        return config_service.update_config(update)
+        updated_config = config_service.update_config(update)
+
+        # Sync anime_directory to settings if it was updated
+        from src.config.settings import settings as app_settings
+
+        anime_dir_changed = False
+        if update.other and update.other.get("anime_directory"):
+            anime_dir = update.other.get("anime_directory")
+            if anime_dir and not app_settings.anime_directory:
+                app_settings.anime_directory = str(anime_dir)
+                anime_dir_changed = True
+                logger.info("Synced anime_directory from config: %s", anime_dir)
+
+        # Start scheduler if anime_directory was just configured
+        if anime_dir_changed:
+            try:
+                from src.server.services.scheduler_service import (
+                    get_scheduler_service,
+                )
+
+                scheduler_svc = get_scheduler_service()
+                logger.info(
+                    "Starting scheduler after anime_directory configuration"
+                )
+                await scheduler_svc.ensure_started()
+                logger.info(
+                    "Scheduler started successfully after config update"
+                )
+            except Exception as sched_exc:
+                logger.warning(
+                    "Failed to start scheduler after config update: %s",
+                    sched_exc,
+                )
+                # Config was already saved, don't fail the request
+
+        return updated_config
+
     except ConfigValidationError as e:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,

src/server/services/scheduler_service.py

@@ -153,6 +153,22 @@ class SchedulerService:
         self._is_running = False
         logger.info("SchedulerService stopped successfully")
 
+    async def ensure_started(self) -> None:
+        """Ensure the scheduler is running (idempotent).
+
+        If already running, returns immediately. Otherwise, starts the scheduler.
+        This method is safe to call multiple times and from multiple callers.
+
+        Raises:
+            SchedulerServiceError: If startup fails (except for already running).
+        """
+        if self._is_running:
+            logger.debug("Scheduler ensure_started called but already running")
+            return
+
+        logger.info("Scheduler ensure_started: starting scheduler")
+        await self.start()
+
     async def trigger_rescan(self) -> bool:
         """Manually trigger a library rescan.