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/blocks/index.js

@@ -9,11 +9,11 @@
 
 export * from './registry'
 
-// ── Wave 1 block definitions ──────────────────────────────────────────
-// import './types/heading'    // added in step 3
-// import './types/richText'
-// import './types/image'
-// import './types/twoColumn'
-// import './types/cta'
-// import './types/divider'
-// import './types/quote'
+// ── Wave 1 block definitions (self-register on import) ─────────────────
+import './types/heading.jsx'
+import './types/richText.jsx'
+import './types/image.jsx'
+import './types/twoColumn.jsx'
+import './types/cta.jsx'
+import './types/divider.jsx'
+import './types/quote.jsx'