feat(ui): Jeff-facing copy + 3:4 inventory thumbs + fixed overlay font

Locked UI/copy pass on proto-per-user-woo-creds (Settings/Woo gate polish out of scope):
- Inventory PNG thumbs at 3:4 contain (Review, Publish preview, Photos ready); stop 1:1 cover squaring
- Dimension overlay labels fixed OVERLAY_FONT_PX=36 for every product
- Page 1–3 Jeff-plain copy; drop Measure red tech essays / px scale rows
- Review: lock SVG, consistent red missing/not-ready, View prompt gated (Settings default off)

frontend/tests/e2e/settings-contrast.spec.ts

@@ -109,7 +109,7 @@ test.describe('Settings contrast (Gitea bug #75 black-on-black)', () => {
   test('Regression: SlabList.svelte / Review.svelte / Publish.svelte / GenerateText.svelte remain unchanged (still pass their existing contrast)', async ({ page }) => {
     const regressionScreens = [
       { name: 'Slabs (dev)', heading: /slabs/i },
-      { name: 'Review (dev)', heading: 'Review to Ready' },
+      { name: 'Review (dev)', heading: 'Review slab' },
       { name: 'Publish (dev)', heading: 'Publish to WooCommerce' },
       { name: 'Generate (dev)', heading: 'Generate text' },
     ];