Feature: SEPA-Export, Push-Notifications, Onboarding + vollständige UI

- Phosphor Icons (Icon.svelte, svg-Registry)
- Schema-Abgleich: alle Felder zwischen PB-Migrations und types.ts konsistent
- Stripe entfernt, SEPA pain.008 XML-Export implementiert (sepa.ts)
- Beiträge: vollständiges CRUD + SEPA-Einzug-Sheet mit Vorschau
- Termine: vollständiges CRUD (upcoming/vergangen, datetime-local)
- Mitglieder: Formulare um alle Felder erweitert (Adresse, SEPA-Mandat, Notizen)
- Nachrichten: Brevo E-Mail via PocketBase-Hook, UI mit Gruppen-Filter
- Push-Notifications: VAPID, Custom Service Worker (injectManifest),
  Subscribe/Send API-Routen, automatische Subscription nach Login
- Onboarding: 3-Schritt-Flow für neue Vereine, Guard im App-Layout
- Makefile: .env wird vollständig zur DS übertragen

app/src/lib/icons/calendar.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><rect width="256" height="256" fill="none"/><rect x="40" y="40" width="176" height="176" rx="8" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><line x1="176" y1="24" x2="176" y2="56" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><line x1="80" y1="24" x2="80" y2="56" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><line x1="40" y1="88" x2="216" y2="88" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><polyline points="88 128 104 120 104 184" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><path d="M138.14,128a16,16,0,1,1,26.64,17.63L136,184h32" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/></svg>