feat: UX improvements — secure webhooks, locale fixes, dynamic languages, UI polish

- Remove top paginator from dashboard events, keep only bottom
- Fix test message locale: pass UI locale to email/matrix bot tests
- Convert webhook auth mode from text input to icon grid selector
- Generate secure UUID tokens for webhook URLs instead of sequential IDs
- Move Recent Payloads into per-provider expandable container (lazy-loaded)
- Make template config languages dynamic via app settings instead of hardcoded
- Change default dev port to 5175

frontend/vite.config.ts

@@ -5,6 +5,7 @@ import { defineConfig } from 'vite';
 export default defineConfig({
 	plugins: [tailwindcss(), sveltekit()],
 	server: {
+		port: 5175,
 		proxy: {
 			'/api': 'http://localhost:8420',
 			'/docs': 'http://localhost:8420',