Add session-based login page and auth for dashboard

dashboard/static/index.html

@@ -50,6 +50,18 @@
     border-radius: 50%;
     background: var(--green);
   }
+  .logout-btn {
+    background: none;
+    border: 1px solid var(--border);
+    color: var(--text-dim);
+    padding: 0.35rem 0.75rem;
+    border-radius: 6px;
+    font-size: 0.8rem;
+    cursor: pointer;
+    margin-left: 1rem;
+    transition: border-color 0.2s, color 0.2s;
+  }
+  .logout-btn:hover { border-color: var(--text-dim); color: var(--text); }
   .container { max-width: 1200px; margin: 0 auto; padding: 1.5rem 2rem; }
 
   /* Agent Cards */
@@ -210,6 +222,7 @@
   <div class="status">
     <div class="dot"></div>
     <span id="agent-count">0 agents</span>
+    <button class="logout-btn" onclick="logout()">Logout</button>
   </div>
 </div>
 
@@ -346,12 +359,21 @@ document.getElementById('modal-overlay').addEventListener('click', e => {
   if (e.target === e.currentTarget) closeModal();
 });
 
+async function logout() {
+  await fetch(API + '/api/logout', {method: 'POST'});
+  window.location.href = '/login';
+}
+
 async function refresh() {
   try {
     const [agentsRes, runsRes] = await Promise.all([
       fetch(API + '/api/agents'),
       fetch(API + '/api/runs?limit=25'),
     ]);
+    if (agentsRes.status === 401 || runsRes.status === 401) {
+      window.location.href = '/login';
+      return;
+    }
     renderAgents(await agentsRes.json());
     renderRuns(await runsRes.json());
   } catch (err) {