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

packages/server/src/notify_bridge_server/api/providers.py

@@ -447,6 +447,7 @@ def _provider_response(p: ServiceProvider) -> dict:
         "name": p.name,
         "icon": p.icon,
         "config": config,
+        "webhook_token": p.webhook_token,
         "created_at": p.created_at.isoformat(),
     }