fix: simplify Electron single instance enforcement

- Remove complex file-based locking that caused crashes
- Use only Electron's built-in requestSingleInstanceLock() API
- Second instances exit immediately with clear messaging
- Existing instance focuses and shows user-friendly dialog
- Prevents database conflicts and resource contention
- Update documentation with simplified approach

Fixes crashes when multiple instances run simultaneously.

electron/src/index.ts

@@ -10,24 +10,11 @@ import { join } from 'path';
 
 import { ElectronCapacitorApp, setupContentSecurityPolicy, setupReloadWatcher } from './setup';
 
-// Single instance enforcement
+// Use Electron's built-in single instance lock
 const gotTheLock = app.requestSingleInstanceLock();
 
 if (!gotTheLock) {
-  console.log('[Electron] Another instance is already running. Exiting...');
-  
-  // Show user-friendly dialog before quitting
-  dialog.showMessageBox({
-    type: 'info',
-    title: 'TimeSafari Already Running',
-    message: 'TimeSafari is already running in another window.',
-    detail: 'Please use the existing TimeSafari window instead of opening a new one.',
-    buttons: ['OK']
-  }).then(() => {
-    app.quit();
-  });
-  
-  // Exit immediately
+  console.log('[Electron] Another instance is already running. Exiting immediately...');
   process.exit(0);
 }
 
@@ -100,7 +87,7 @@ autoUpdater.on('error', (error) => {
   // Initialize our app, build windows, and load content.
   await myCapacitorApp.init();
   
-  // Handle second instance launch (focus existing window)
+  // Handle second instance launch (focus existing window and show dialog)
   app.on('second-instance', (event, commandLine, workingDirectory) => {
     console.log('[Electron] Second instance attempted to launch');
     
@@ -111,6 +98,17 @@ autoUpdater.on('error', (error) => {
         mainWindow.restore();
       }
       mainWindow.focus();
+      
+      // Show user-friendly dialog to inform about single instance
+      dialog.showMessageBox(mainWindow, {
+        type: 'info',
+        title: 'TimeSafari Already Running',
+        message: 'TimeSafari is already running in another window.',
+        detail: 'Please use this existing TimeSafari window instead of opening a new one.',
+        buttons: ['OK']
+      }).catch((error) => {
+        console.error('[Electron] Error showing dialog:', error);
+      });
     }
   });