feat: Add subscription UI components

- Add Subscription interface to auth store
- Add subscription computed properties (isTrialActive, isExpired, etc.)
- Add SubscriptionBanner component (trial warning, expired notice)
- Add SubscriptionExpiredView (blocked access screen)
- Update AppLayout to show banner
- Update router to redirect expired subscriptions

src/components/SubscriptionBanner.vue

@@ -0,0 +1,58 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { useAuthStore } from '@/stores/auth'
+
+const authStore = useAuthStore()
+
+const bannerType = computed(() => {
+  if (authStore.isSubscriptionExpired) return 'expired'
+  if (authStore.showTrialWarning) return 'trial-warning'
+  if (authStore.isTrialActive) return 'trial'
+  return null
+})
+
+const bannerClass = computed(() => {
+  switch (bannerType.value) {
+    case 'expired': return 'bg-red-600 text-white'
+    case 'trial-warning': return 'bg-yellow-500 text-yellow-900'
+    case 'trial': return 'bg-blue-500 text-white'
+    default: return ''
+  }
+})
+
+const message = computed(() => {
+  const days = authStore.trialDaysRemaining
+  
+  switch (bannerType.value) {
+    case 'expired':
+      return authStore.subscription?.status === 'paused' 
+        ? '⚠️ Ihr Account wurde pausiert. Bitte kontaktieren Sie den Support.'
+        : '⚠️ Ihre Testphase ist abgelaufen. Bitte wählen Sie ein Abonnement.'
+    case 'trial-warning':
+      return `⏰ Nur noch ${days} Tag${days === 1 ? '' : 'e'} in der Testphase! Jetzt Abo wählen.`
+    case 'trial':
+      return `🎉 Testphase: Noch ${days} Tag${days === 1 ? '' : 'e'} kostenlos testen`
+    default:
+      return ''
+  }
+})
+
+const showBanner = computed(() => bannerType.value !== null)
+</script>
+
+<template>
+  <div 
+    v-if="showBanner" 
+    :class="['px-4 py-2 text-center text-sm font-medium', bannerClass]"
+  >
+    {{ message }}
+    <a 
+      v-if="bannerType === 'expired' || bannerType === 'trial-warning'"
+      href="https://secu.kronos-soulution.de/#preise" 
+      target="_blank"
+      class="ml-2 underline font-bold hover:no-underline"
+    >
+      Preise ansehen →
+    </a>
+  </div>
+</template>