Fix stale DB connections, add Why Bourbonacci section, harden auth

- Add pool_pre_ping and pool_recycle to prevent lost connection errors on idle pool
- Add Why Bourbonacci card to about page
- Redirect to login on 401 in API layer
- Check JWT expiry in isLoggedIn instead of just token presence

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

frontend/js/api.js

@@ -26,6 +26,13 @@ const API = (() => {
 
     const data = await res.json().catch(() => null);
 
+    if (res.status === 401) {
+      localStorage.removeItem('bb_token');
+      localStorage.removeItem('bb_user');
+      window.location.href = '/login.html';
+      return;
+    }
+
     if (!res.ok) {
       const msg = data?.detail || `HTTP ${res.status}`;
       throw new Error(Array.isArray(msg) ? msg.map(e => e.msg).join(', ') : msg);