feat(notify-bridge): phase 7 - frontend restructuring

Notify Bridge frontend with SvelteKit 2 + Svelte 5 + Tailwind CSS v4:
- Auth: login page, setup page, auth state management with $state runes
- Theme: dark/light toggle with localStorage persistence
- i18n: EN/RU translations with reactive $state-based t() function
- Routes: dashboard, providers, trackers, targets, tracking-configs,
  template-configs, telegram-bots, users (stubs for configs pages)
- Providers page: list with card grid, "Add Provider" button
- API client: JWT auth, auto-redirect on 401, typed request helpers
- Branding: "Notify Bridge" throughout, Observatory theme colors

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/tracking-configs/+page.svelte

@@ -0,0 +1,8 @@
+<script>
+	import { t } from '$lib/i18n/index.svelte.ts';
+</script>
+
+<div class="p-6 max-w-5xl mx-auto">
+	<h1 class="text-2xl font-bold mb-6">{t('nav.trackingConfigs')}</h1>
+	<p class="text-muted-foreground">Tracking configuration management — coming soon.</p>
+</div>