feat: implement auto-sync scheduler for LoTW and DCL

Add automatic synchronization scheduler that allows users to configure
periodic sync intervals for LoTW and DCL via the settings page.

Features:
- Users can enable/disable auto-sync per service (LoTW/DCL)
- Configurable sync intervals (1-720 hours)
- Settings page UI for managing auto-sync preferences
- Dashboard shows upcoming scheduled auto-sync jobs
- Scheduler runs every minute, triggers syncs when due
- Survives server restarts via database persistence
- Graceful shutdown support (SIGINT/SIGTERM)

Backend:
- New autoSyncSettings table with user preferences
- auto-sync.service.js for CRUD operations and scheduling logic
- scheduler.service.js for periodic tick processing
- API endpoints: GET/PUT /auto-sync/settings, GET /auto-sync/scheduler/status

Frontend:
- Auto-sync settings section in settings page
- Upcoming auto-sync section on dashboard with scheduled job cards
- Purple-themed UI for scheduled jobs with countdown animation

Co-Authored-By: Claude <noreply@anthropic.com>

src/backend/index.js

@@ -43,6 +43,16 @@ import {
   getAwardProgressDetails,
   getAwardEntityBreakdown,
 } from './services/awards.service.js';
+import {
+  getAutoSyncSettings,
+  updateAutoSyncSettings,
+} from './services/auto-sync.service.js';
+import {
+  startScheduler,
+  stopScheduler,
+  getSchedulerStatus,
+  triggerSchedulerTick,
+} from './services/scheduler.service.js';
 
 /**
  * Main backend application
@@ -1398,6 +1408,133 @@ const app = new Elysia()
     }
   })
 
+  /**
+   * ================================================================
+   * AUTO-SYNC SETTINGS ROUTES
+   * ================================================================
+   * All auto-sync routes require authentication
+   */
+
+  /**
+   * GET /api/auto-sync/settings
+   * Get user's auto-sync settings (requires authentication)
+   */
+  .get('/api/auto-sync/settings', async ({ user, set }) => {
+    if (!user) {
+      set.status = 401;
+      return { success: false, error: 'Unauthorized' };
+    }
+
+    try {
+      const settings = await getAutoSyncSettings(user.id);
+
+      return {
+        success: true,
+        settings,
+      };
+    } catch (error) {
+      logger.error('Error fetching auto-sync settings', { error: error.message, userId: user.id });
+      set.status = 500;
+      return {
+        success: false,
+        error: 'Failed to fetch auto-sync settings',
+      };
+    }
+  })
+
+  /**
+   * PUT /api/auto-sync/settings
+   * Update user's auto-sync settings (requires authentication)
+   */
+  .put(
+    '/api/auto-sync/settings',
+    async ({ user, body, set }) => {
+      if (!user) {
+        set.status = 401;
+        return { success: false, error: 'Unauthorized' };
+      }
+
+      try {
+        const settings = await updateAutoSyncSettings(user.id, body);
+
+        return {
+          success: true,
+          settings,
+          message: 'Auto-sync settings updated successfully',
+        };
+      } catch (error) {
+        logger.error('Error updating auto-sync settings', { error: error.message, userId: user.id });
+        set.status = 400;
+        return {
+          success: false,
+          error: error.message,
+        };
+      }
+    },
+    {
+      body: t.Object({
+        lotwEnabled: t.Optional(t.Boolean()),
+        lotwIntervalHours: t.Optional(t.Number()),
+        dclEnabled: t.Optional(t.Boolean()),
+        dclIntervalHours: t.Optional(t.Number()),
+      }),
+    }
+  )
+
+  /**
+   * GET /api/auto-sync/scheduler/status
+   * Get scheduler status (admin only)
+   */
+  .get('/api/auto-sync/scheduler/status', async ({ user, set }) => {
+    if (!user || !user.isAdmin) {
+      set.status = !user ? 401 : 403;
+      return { success: false, error: !user ? 'Unauthorized' : 'Admin access required' };
+    }
+
+    try {
+      const status = getSchedulerStatus();
+
+      return {
+        success: true,
+        scheduler: status,
+      };
+    } catch (error) {
+      logger.error('Error fetching scheduler status', { error: error.message, userId: user.id });
+      set.status = 500;
+      return {
+        success: false,
+        error: 'Failed to fetch scheduler status',
+      };
+    }
+  })
+
+  /**
+   * POST /api/auto-sync/scheduler/trigger
+   * Manually trigger scheduler tick (admin only, for testing)
+   */
+  .post('/api/auto-sync/scheduler/trigger', async ({ user, set }) => {
+    if (!user || !user.isAdmin) {
+      set.status = !user ? 401 : 403;
+      return { success: false, error: !user ? 'Unauthorized' : 'Admin access required' };
+    }
+
+    try {
+      await triggerSchedulerTick();
+
+      return {
+        success: true,
+        message: 'Scheduler tick triggered successfully',
+      };
+    } catch (error) {
+      logger.error('Error triggering scheduler tick', { error: error.message, userId: user.id });
+      set.status = 500;
+      return {
+        success: false,
+        error: 'Failed to trigger scheduler tick',
+      };
+    }
+  })
+
   // Serve static files and SPA fallback for all non-API routes
   .get('/*', ({ request }) => {
     const url = new URL(request.url);
@@ -1554,3 +1691,21 @@ logger.info('Server started', {
   nodeEnv: process.env.NODE_ENV || 'unknown',
   logLevel: LOG_LEVEL,
 });
+
+// Start the auto-sync scheduler
+startScheduler();
+
+// Graceful shutdown handlers
+const gracefulShutdown = async (signal) => {
+  logger.info(`Received ${signal}, shutting down gracefully...`);
+
+  // Stop the scheduler
+  await stopScheduler();
+
+  logger.info('Graceful shutdown complete');
+  process.exit(0);
+};
+
+// Handle shutdown signals
+process.on('SIGINT', () => gracefulShutdown('SIGINT'));
+process.on('SIGTERM', () => gracefulShutdown('SIGTERM'));