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/+page.svelte

@@ -319,10 +319,6 @@
 		</div>
 	{/snippet}
 
-	<div class="mb-3">
-		{@render paginator()}
-	</div>
-
 	{#if eventsLoading}
 		<Card><p class="text-sm text-center py-4" style="color: var(--color-muted-foreground);">{t('dashboard.loadingEvents')}</p></Card>
 	{:else if status.recent_events.length === 0}