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/src/routes/template-configs/+page.svelte

@@ -4,7 +4,7 @@
 	import { api } from '$lib/api';
 	import { t } from '$lib/i18n';
 	import { sanitizePreview } from '$lib/sanitize';
-	import { templateConfigsCache, capabilitiesCache } from '$lib/stores/caches.svelte';
+	import { templateConfigsCache, capabilitiesCache, supportedLocalesCache } from '$lib/stores/caches.svelte';
 	import PageHeader from '$lib/components/PageHeader.svelte';
 	import Card from '$lib/components/Card.svelte';
 	import Loading from '$lib/components/Loading.svelte';
@@ -57,7 +57,7 @@
 	let slotFilter = $state('');
 	let showPreviewFor = $state<Set<string>>(new Set());
 
-	const LOCALES = ['en', 'ru'] as const;
+	let LOCALES = $derived(supportedLocalesCache.items);
 	let activeLocale = $state<string>('en');
 
 	function toggleSlot(key: string) {
@@ -202,6 +202,7 @@
 				templateConfigsCache.fetch(true),
 				api('/template-configs/variables'),
 				capabilitiesCache.fetch(),
+				supportedLocalesCache.fetch(),
 			]);
 		} catch (err: any) { error = err.message || t('common.loadError'); snackError(error); }
 		finally { loaded = true; highlightFromUrl(); }