feat: add server persistence for rosary streak

- Add RosaryStreak MongoDB model for logged-in users
- Add /api/glaube/rosary-streak GET/POST endpoints
- Sync streak to server when logged in, merge local/server data
- Auto-sync when coming back online (PWA offline support)
- Falls back to localStorage for guests

src/lib/components/StreakCounter.svelte

@@ -2,7 +2,20 @@
 import { browser } from '$app/environment';
 import { getRosaryStreak } from '$lib/stores/rosaryStreak.svelte';
 
+interface Props {
+	user?: { nickname?: string } | null;
+}
+
+let { user = null }: Props = $props();
+
 const streak = browser ? getRosaryStreak() : null;
+
+// Sync with server when user is logged in
+$effect(() => {
+	if (browser && streak) {
+		streak.setLoggedIn(!!user?.nickname);
+	}
+});
 </script>
 
 <div class="streak-container">