Add Wave 1 block renderers + editors (page builder step 3, client half)

Client block registry now carries a renderer, edit form, palette label/icon,
and defaults for all seven Wave 1 blocks (self-registering via
client/src/blocks/types/*): heading, rich_text, image, two_column, cta,
divider, quote.

- BlockRenderer + BlockList render stored blocks via the registry (respect
  `visible`, tolerate unknown types), reading getBlock from ./registry to
  avoid the index -> twoColumn -> BlockRenderer cycle.
- editorKit: shared Field/TextField/TextAreaField/SelectField styled with the
  existing admin form classes; rich_text editor reuses RichTextEditor
  (variant post), image editor reuses the shared uploader.
- two_column editor is a mini per-column canvas (add from the leaf-only
  palette, edit via each block's registry editor, reorder, remove).
- theme.css: public block styles (heading/image alignment/cta/quote/
  two-column responsive grid) + column sub-block editor styles.

Verified: all 11 modules transform cleanly under esbuild. Full visual
verification comes with the builder UI (step 5) + public route (step 6).

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

client/src/styles/theme.css

@@ -740,3 +740,147 @@ button[disabled] {
     grid-template-columns: 1fr;
   }
 }
+
+/* ===== CMS page builder — public block rendering ===== */
+/* Vertical rhythm between top-level blocks on a rendered page. */
+.page-blocks > * + * {
+  margin-top: 26px;
+}
+.page-heading {
+  font-family: var(--serif, Georgia, serif);
+  color: var(--ink);
+  line-height: 1.2;
+}
+.page-divider {
+  border: none;
+  border-top: 1px solid var(--line);
+  margin: 8px 0;
+}
+/* image block */
+.page-image {
+  margin: 0;
+}
+.page-image img {
+  max-width: 100%;
+  border-radius: 8px;
+  border: 1px solid var(--line);
+  display: block;
+}
+.page-image figcaption {
+  margin-top: 8px;
+  color: var(--muted);
+  font-family: var(--sans);
+  font-size: 0.82rem;
+}
+.page-image--center {
+  text-align: center;
+}
+.page-image--center img,
+.page-image--center figcaption {
+  margin-left: auto;
+  margin-right: auto;
+}
+.page-image--right {
+  text-align: right;
+}
+.page-image--right img,
+.page-image--right figcaption {
+  margin-left: auto;
+}
+.page-image--full img {
+  width: 100%;
+}
+/* cta block */
+.page-cta-wrap {
+  display: flex;
+}
+.page-cta--secondary {
+  background: transparent;
+  color: var(--ink);
+}
+/* quote block */
+.page-quote {
+  margin: 0;
+  border-left: 3px solid var(--accent);
+  padding: 4px 0 4px 20px;
+}
+.page-quote blockquote {
+  margin: 0;
+  font-size: 1.15rem;
+  line-height: 1.5;
+  color: var(--ink);
+  font-style: italic;
+}
+.page-quote figcaption {
+  margin-top: 8px;
+  color: var(--muted);
+  font-family: var(--sans);
+  font-size: 0.85rem;
+}
+/* two-column block */
+.page-two-column {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 32px;
+}
+.page-column > * + * {
+  margin-top: 18px;
+}
+@media (max-width: 720px) {
+  .page-two-column {
+    grid-template-columns: 1fr;
+  }
+}
+
+/* ===== CMS page builder — column sub-block editor ===== */
+.pb-two-column-editor {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 16px;
+}
+@media (max-width: 720px) {
+  .pb-two-column-editor {
+    grid-template-columns: 1fr;
+  }
+}
+.pb-column-editor {
+  border: 1px solid var(--line);
+  border-radius: 8px;
+  padding: 12px;
+  background: var(--panel-flat, transparent);
+}
+.pb-column-head {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 8px;
+  margin-bottom: 10px;
+}
+.pb-add-select {
+  width: auto;
+  padding: 6px 10px;
+  font-size: 0.82rem;
+}
+.pb-subblock {
+  border: 1px solid var(--line);
+  border-radius: 8px;
+  padding: 10px;
+  margin-top: 10px;
+  background: var(--bg);
+}
+.pb-subblock-head {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 8px;
+}
+.pb-subblock-actions {
+  display: flex;
+  gap: 4px;
+}
+.pb-mini {
+  min-width: 28px;
+  padding: 3px 8px;
+  font-size: 0.8rem;
+  line-height: 1;
+}