Implement Phase 5: reconciliation, SignalR notifications, payees, splits & plugins

Add full frontend UI for five backend features: bank reconciliation (3-step
stepper workflow), payee management (CRUD with alias chips), transaction splits
(expandable rows + split editor), plugins (card grid), and real-time SignalR
notifications (bell dropdown with badge). Fix backend PayeeResponse to expose
alias IDs for deletion.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/views/plugins/PluginsView.vue

@@ -1,6 +1,47 @@
 <template>
   <div>
     <h1 class="text-h4 mb-4">Plugins</h1>
-    <v-card><v-card-text><p class="text-medium-emphasis">Plugin marketplace coming in Phase 5. Extend Purrse with community-built integrations and features.</p></v-card-text></v-card>
+
+    <v-progress-linear v-if="loading" indeterminate color="primary" class="mb-4" />
+
+    <v-alert v-if="!loading && plugins.length === 0" type="info" variant="tonal" class="mb-4">
+      No plugins installed. Plugins extend Purrse with additional features and integrations.
+    </v-alert>
+
+    <v-row v-if="plugins.length > 0">
+      <v-col v-for="plugin in plugins" :key="plugin.id" cols="12" sm="6" md="4">
+        <v-card>
+          <v-card-item>
+            <template v-slot:prepend>
+              <v-icon size="large" color="primary">mdi-puzzle</v-icon>
+            </template>
+            <v-card-title>{{ plugin.name }}</v-card-title>
+            <v-card-subtitle>v{{ plugin.version }}</v-card-subtitle>
+          </v-card-item>
+          <v-card-text>{{ plugin.description }}</v-card-text>
+        </v-card>
+      </v-col>
+    </v-row>
   </div>
 </template>
+
+<script setup lang="ts">
+import { ref, onMounted } from 'vue'
+import { pluginsApi } from '@/services/plugins'
+import type { Plugin } from '@/types'
+
+const plugins = ref<Plugin[]>([])
+const loading = ref(false)
+
+onMounted(async () => {
+  loading.value = true
+  try {
+    const { data } = await pluginsApi.getAll()
+    plugins.value = data
+  } catch {
+    // silently handle - empty state shown
+  } finally {
+    loading.value = false
+  }
+})
+</script>