fix: Custom cron input and auto-sync rescheduling

- Fixed custom cron input field to be properly editable with autoFocus
- Added helpful cron examples and better validation feedback
- Fixed cron validation to work with 5-field expressions (node-cron format)
- Added auto-sync rescheduling when settings are saved via API route
- Improved user experience with better error handling and examples

The custom cron input now works properly and auto-sync will reschedule
immediately when settings are saved, including custom cron expressions.

src/app/_components/GeneralSettingsModal.tsx

@@ -885,6 +885,8 @@ export function GeneralSettingsModal({ isOpen, onClose }: GeneralSettingsModalPr
                             value={syncIntervalCron}
                             onChange={(e) => handleCronChange(e.target.value)}
                             className="w-full"
+                            autoFocus
+                            onFocus={() => setCronValidationError('')}
                           />
                           {cronValidationError && (
                             <p className="text-sm text-red-500 mt-1">{cronValidationError}</p>
@@ -896,6 +898,16 @@ export function GeneralSettingsModal({ isOpen, onClose }: GeneralSettingsModalPr
                             </a>{' '}
                             for examples
                           </p>
+                          <div className="mt-2 p-2 bg-muted rounded text-xs">
+                            <p className="font-medium mb-1">Common examples:</p>
+                            <ul className="space-y-1 text-muted-foreground">
+                              <li>• <code>* * * * *</code> - Every minute</li>
+                              <li>• <code>0 * * * *</code> - Every hour</li>
+                              <li>• <code>0 */6 * * *</code> - Every 6 hours</li>
+                              <li>• <code>0 0 * * *</code> - Every day at midnight</li>
+                              <li>• <code>0 0 * * 0</code> - Every Sunday at midnight</li>
+                            </ul>
+                          </div>
                         </div>
                       )}
                     </div>

src/app/api/settings/auto-sync/route.ts

@@ -71,7 +71,7 @@ export async function POST(request: NextRequest) {
         );
       }
 
-      if (!isValidCron(settings.syncIntervalCron)) {
+      if (!isValidCron(settings.syncIntervalCron, { seconds: false })) {
         return NextResponse.json(
           { error: 'Invalid cron expression' },
           { status: 400 }
@@ -158,6 +158,23 @@ export async function POST(request: NextRequest) {
     // Write back to .env file
     fs.writeFileSync(envPath, envContent);
 
+    // Reschedule auto-sync service with new settings
+    try {
+      const { AutoSyncService } = await import('../../../../server/services/autoSyncService.js');
+      const autoSyncService = new AutoSyncService();
+      
+      if (settings.autoSyncEnabled) {
+        autoSyncService.scheduleAutoSync();
+        console.log('Auto-sync rescheduled with new settings');
+      } else {
+        autoSyncService.stopAutoSync();
+        console.log('Auto-sync stopped');
+      }
+    } catch (error) {
+      console.error('Error rescheduling auto-sync service:', error);
+      // Don't fail the request if rescheduling fails
+    }
+
     return NextResponse.json({ 
       success: true, 
       message: 'Auto-sync settings saved successfully' 

src/server/services/autoSyncService.js

@@ -191,8 +191,8 @@ export class AutoSyncService {
       cronExpression = intervalMap[settings.syncIntervalPredefined] || '0 * * * *';
     }
     
-    // Validate cron expression
-    if (!cronValidator.isValidCron(cronExpression)) {
+    // Validate cron expression (5-field format for node-cron)
+    if (!cronValidator.isValidCron(cronExpression, { seconds: false })) {
       console.error('Invalid cron expression:', cronExpression);
       return;
     }