Add recent sessions display on home page

Users can now see and click on previous sessions from the home page without
having to create a new session. Shows up to 6 most recent sessions with:
- Session ID and status (created/completed)
- First 100 chars of prompt
- Session creation date

Features:
- Fetches sessions from new GET /api/collaborate endpoint
- Clickable cards to open existing sessions
- Beautiful glassmorphic cards with hover effects
- Responsive grid layout

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/components/CollaborativeInput.vue

@@ -1,5 +1,5 @@
 <script setup>
-import { ref, computed } from 'vue'
+import { ref, computed, onMounted } from 'vue'
 import { useCollaborationStore } from '../stores/collaboration'
 
 const emit = defineEmits(['session-created'])
@@ -10,6 +10,25 @@ const prompt = ref('')
 const contextFile = ref(null)
 const agentCount = ref(7)
 const isCreating = ref(false)
+const previousSessions = ref([])
+const loadingPreviousSessions = ref(false)
+
+onMounted(async () => {
+  loadingPreviousSessions.value = true
+  try {
+    const response = await fetch('/api/collaborate')
+    const data = await response.json()
+    previousSessions.value = data.sessions || []
+  } catch (error) {
+    console.error('Error loading previous sessions:', error)
+  } finally {
+    loadingPreviousSessions.value = false
+  }
+})
+
+const handleOpenSession = (sessionId) => {
+  emit('session-created', { sessionId })
+}
 
 const agentOptions = computed(() => {
   return Array.from({ length: 48 }, (_, i) => ({
@@ -182,6 +201,27 @@ const removeFile = () => {
         </button>
       </form>
 
+      <!-- Previous Sessions -->
+      <div v-if="previousSessions.length > 0" class="previous-sessions-section">
+        <h2>Recent Sessions</h2>
+        <div class="sessions-grid">
+          <div
+            v-for="session in previousSessions.slice(0, 6)"
+            :key="session.sessionId"
+            @click="handleOpenSession(session.sessionId)"
+            class="session-card"
+            :class="{ 'status-completed': session.status === 'completed' }"
+          >
+            <div class="session-header">
+              <span class="session-id">#{{ session.sessionId }}</span>
+              <span class="session-status">{{ session.status }}</span>
+            </div>
+            <p class="session-prompt">{{ session.prompt.substring(0, 100) }}...</p>
+            <p class="session-date">{{ new Date(session.createdAt).toLocaleDateString() }}</p>
+          </div>
+        </div>
+      </div>
+
       <footer class="footer">
         <p>Typical session: 2-5 rounds for complete consensus. Output format: Markdown</p>
       </footer>
@@ -501,6 +541,82 @@ const removeFile = () => {
   font-size: 0.95rem;
 }
 
+.previous-sessions-section {
+  margin-top: 3rem;
+  padding-top: 2rem;
+  border-top: 1px solid rgba(102, 126, 234, 0.2);
+}
+
+.previous-sessions-section h2 {
+  font-size: 1.5rem;
+  margin-bottom: 1.5rem;
+  color: rgba(102, 126, 234, 0.9);
+}
+
+.sessions-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
+  gap: 1rem;
+}
+
+.session-card {
+  padding: 1.25rem;
+  background: rgba(255, 255, 255, 0.06);
+  border: 1px solid rgba(102, 126, 234, 0.3);
+  border-radius: 12px;
+  cursor: pointer;
+  transition: all 0.3s ease;
+  backdrop-filter: blur(10px);
+}
+
+.session-card:hover {
+  background: rgba(102, 126, 234, 0.15);
+  border-color: rgba(102, 126, 234, 0.5);
+  transform: translateY(-2px);
+  box-shadow: 0 8px 24px rgba(102, 126, 234, 0.2);
+}
+
+.session-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 0.75rem;
+}
+
+.session-id {
+  font-weight: 700;
+  color: rgba(102, 126, 234, 0.9);
+  font-size: 1.1rem;
+}
+
+.session-status {
+  padding: 0.25rem 0.75rem;
+  background: rgba(76, 175, 80, 0.25);
+  color: rgba(76, 175, 80, 0.9);
+  border-radius: 20px;
+  font-size: 0.75rem;
+  font-weight: 600;
+  text-transform: capitalize;
+}
+
+.session-card.status-completed .session-status {
+  background: rgba(76, 175, 80, 0.3);
+  color: rgba(76, 175, 80, 0.95);
+}
+
+.session-prompt {
+  margin: 0.75rem 0;
+  color: rgba(255, 255, 255, 0.7);
+  font-size: 0.9rem;
+  line-height: 1.4;
+}
+
+.session-date {
+  margin: 0;
+  color: rgba(255, 255, 255, 0.5);
+  font-size: 0.85rem;
+}
+
 @media (max-width: 768px) {
   .collaborative-input {
     padding: 1rem;