Add page builder admin UI + public page route (step 5 + step 6 client)

- PagesAdmin: list view of pages (title/slug/status/protected/updated) with
  new/edit navigation and a View link to the live page.
- PageBuilder: full-page block canvas — palette (adds any registered block),
  per-block editor cards with show/hide, up/down + native drag reorder, and
  remove; Content / Settings tabs; SEO metadata + layout/nav settings panels;
  publish/unpublish; protect (PATCH) and password-gated unprotect (modal);
  draft preview (mints a token, opens /preview/:id/:token); delete (blocked
  while protected). Surfaces server block-validation details on save.
- CmsPage: public renderer for /:slug (published; staff see drafts) and the
  token-gated /preview/:id/:token, rendering blocks via BlockList and
  reflecting the page title/meta.
- Routing: /:slug catch-all after all named routes + /preview/:id/:token
  outside the maintenance gate; admin /admin/pages, /pages/new, /pages/:id.
- api client: public page/pagePreview + admin pages CRUD/unprotect/preview.
- AdminLayout: "Pages" nav entry (Content group) with icon.
- theme.css: builder canvas + preview-banner + shell-wide styles.

Client builds clean (216 modules).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/routes/admin/views/PagesAdmin.jsx

@@ -0,0 +1,91 @@
+import { useCallback, useState } from 'react'
+import { useNavigate } from 'react-router-dom'
+import { Loading, ErrorState } from '../../../components/PageState.jsx'
+import { useAsync } from '../../../lib/useAsync.js'
+import { shortDate } from '../../../lib/format.js'
+import { api } from '../../../api/client.js'
+
+// List of CMS pages. Create/edit open the full-page block builder; the builder
+// owns save/delete/publish so this view is read-only navigation.
+export default function PagesAdmin() {
+  const navigate = useNavigate()
+  const [tick] = useState(0)
+  const { loading, error, data } = useAsync(() => api.admin.listPages(), [tick])
+  const pages = data || []
+
+  const openNew = useCallback(() => navigate('/admin/pages/new'), [navigate])
+
+  return (
+    <section>
+      <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', gap: 14, marginBottom: 18 }}>
+        <p className="sans dim" style={{ margin: 0, fontSize: '0.85rem' }}>
+          Compose pages from blocks. A published page is live at <code>/its-slug</code>.
+        </p>
+        <button onClick={openNew} className="btn btn-primary btn-sq">
+          + New page
+        </button>
+      </div>
+
+      {loading && <Loading />}
+      {error && <ErrorState message="Could not load pages." />}
+
+      {!loading && !error && (
+        <div className="panel-flat">
+          <table className="adm-table">
+            <thead>
+              <tr>
+                <th className="adm-th">Title</th>
+                <th className="adm-th">Slug</th>
+                <th className="adm-th">Status</th>
+                <th className="adm-th">Updated</th>
+                <th className="adm-th" />
+              </tr>
+            </thead>
+            <tbody>
+              {pages.length === 0 && (
+                <tr>
+                  <td className="adm-td" colSpan={5} style={{ color: 'var(--muted)' }}>
+                    No pages yet — create your first one.
+                  </td>
+                </tr>
+              )}
+              {pages.map((p) => (
+                <tr key={p.id}>
+                  <td className="adm-td" style={{ color: 'var(--head)' }}>
+                    {p.title}
+                    {p.protected && (
+                      <span title="Protected" style={{ marginLeft: 8 }}>🔒</span>
+                    )}
+                  </td>
+                  <td className="adm-td dim">/{p.slug}</td>
+                  <td className="adm-td">
+                    <span className={`badge ${p.status === 'published' ? 'badge-pub' : 'badge-draft'}`}>
+                      {p.status === 'published' ? 'Published' : 'Draft'}
+                    </span>
+                  </td>
+                  <td className="adm-td dim">{shortDate(p.updatedAt)}</td>
+                  <td className="adm-td" style={{ textAlign: 'right' }}>
+                    {p.status === 'published' && (
+                      <a
+                        className="link-accent"
+                        href={`/${p.slug}`}
+                        target="_blank"
+                        rel="noreferrer"
+                        style={{ marginRight: 14 }}
+                      >
+                        View
+                      </a>
+                    )}
+                    <span className="link-accent" onClick={() => navigate(`/admin/pages/${p.id}`)}>
+                      Edit
+                    </span>
+                  </td>
+                </tr>
+              ))}
+            </tbody>
+          </table>
+        </div>
+      )}
+    </section>
+  )
+}