Add user management with admin and viewer roles

- data/users.json store; existing single account migrates to first admin
- Roles: admin (settings, import, users) and viewer (read-only, own password)
- Live role/disabled lookup; per-user session epoch so password changes,
  resets and disabling sign that user out everywhere
- Login brute-force lockout (5 fails -> 5 min), constant-time unknown-user check
- /api/users CRUD with last-admin and self-lockout safeguards
- Account page (own password + admin user management); role-aware header
- Min password length 8; recovery token resets the primary admin and clears lockouts

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/public/dashboard-settings.html

@@ -88,6 +88,7 @@ button.primary:disabled { opacity: 0.5; cursor: not-allowed; }
   <div><h1>Settings</h1></div>
   <div class="header-right">
     <a href="/dashboard" class="nav-link">← Dashboard</a>
+    <a href="/dashboard/account" class="nav-link">Account</a>
     <a href="/dashboard/logout" class="nav-link">Sign out</a>
   </div>
 </div>
@@ -204,17 +205,12 @@ button.primary:disabled { opacity: 0.5; cursor: not-allowed; }
     </div>
   </div>
 
-  <!-- Change Password -->
+  <!-- Account -->
   <div class="section">
-    <div class="section-hdr">Change Password</div>
-    <div class="settings-grid">
-      <div><label>Current Password</label><input id="pwCurrent" type="password" autocomplete="current-password"></div>
-      <div><label>New Password (min 6 chars)</label><input id="pwNew" type="password" autocomplete="new-password"></div>
-    </div>
-    <div class="settings-actions">
-      <button class="primary" id="changePwBtn">Change Password</button>
-      <span id="pwMsg" class="save-msg"></span>
-    </div>
+    <div class="section-hdr">Account &amp; Users</div>
+    <p class="hint" style="margin:0 0 0.85rem">Change your password and manage who can sign in (admin and viewer accounts).</p>
+    <a class="export-link" href="/dashboard/account">Open account &amp; users →</a>
+  </div>
   </div>
 
 </div>
@@ -413,28 +409,6 @@ async function pollBackfill() {
 
 document.getElementById('backfillBtn').addEventListener('click', startBackfill);
 
-// ── Change Password ───────────────────────────────────────────────────────────
-document.getElementById('changePwBtn').addEventListener('click', async () => {
-  const cur = document.getElementById('pwCurrent')?.value;
-  const nw = document.getElementById('pwNew')?.value;
-  const msg = document.getElementById('pwMsg');
-  if (!cur || !nw || nw.length < 6) { msg.textContent = 'Fill both fields (min 6 chars)'; msg.className = 'save-msg err'; return; }
-  try {
-    const r = await fetch('/api/dashboard/change-password', {
-      method: 'POST', headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ currentPassword: cur, newPassword: nw })
-    });
-    if (r.ok) {
-      msg.textContent = 'Password changed'; msg.className = 'save-msg';
-      document.getElementById('pwCurrent').value = '';
-      document.getElementById('pwNew').value = '';
-    } else {
-      const e = await r.json();
-      msg.textContent = e.error || 'Error'; msg.className = 'save-msg err';
-    }
-    setTimeout(() => msg.textContent = '', 4000);
-  } catch { msg.textContent = 'Error'; msg.className = 'save-msg err'; }
-});
 
 // ── Scroll shadow ─────────────────────────────────────────────────────────────
 window.addEventListener('scroll', () => {