feat: add update instructions dialog, email notifications, and capture date sorting

- Add Update Instructions Dialog with environment-specific commands (Docker/Git/Standalone)
- Add email notification settings for new version alerts
- Add "Sort by Capture Date" option using EXIF metadata extraction
- Fix E2E tests by loading environment variables via dotenv
- Add test-images/ and backend/*.db to .gitignore

Closes #181

playwright.config.ts

@@ -1,4 +1,8 @@
 import { defineConfig, devices } from '@playwright/test';
+import dotenv from 'dotenv';
+
+// Load environment variables from .env file
+dotenv.config();
 
 export default defineConfig({
   testDir: 'tests/e2e',