feat(greenfield): rebuild SlabUploader M1-M3 on clean foundation, all gates green

Clean re-implementation of the full product (not a port of the old M3 tree):
- P0 foundation: 13-table schema + per-call sqlite factory (thread-safe),
  FastAPI app (health, JSON logging + secret redaction, CORS, startup guard).
- P1 M1 Capture: mask/sheetKeep, geometry/rect (min-area rect), measure,
  png crop/inventory/overlay, EXIF decodeOrientedBitmap.
- P2 M2 Photos: stateful capture session (batch, pick-cal, apply mask/crop
  to batch) + photos-ready lineup.
- P3 M3 Create: real backend (crypto, woo client, taxonomy sync, pricing,
  inference Call1/Call2, review, publish, settings, slabs, photos) + real FE
  review/publish/settings screens consuming the API (no hardcoded Woo ids).
- P4 gate exit: check_requirements + check_coverage both exit 0
  (137/155 IDs, 0 gaps); backend 130/130, frontend 150/150, build green.

Cite: docs/REQUIREMENTS.md (155 rows), docs/MILESTONES.md M1-M3.

frontend/src/publish/PublishPanel.svelte

@@ -0,0 +1,81 @@
+<script lang="ts">
+  import { createEventDispatcher } from 'svelte';
+  import { apiFetch, ApiError, isRecoverable } from '../lib/api';
+  import type { SlabDraft } from '../lib/types';
+
+  export let slab: SlabDraft;
+  const dispatch = createEventDispatcher<{
+    success: { id: number | null; draft: boolean };
+    back: void;
+  }>();
+
+  interface PublishOk {
+    ok: boolean;
+    status: string;
+    woo_product_id: number;
+    draft: boolean;
+  }
+
+  let status = '';
+  let result: PublishOk | null = null;
+  let error = '';
+  let recoverable = false;
+
+  async function attemptPublish() {
+    status = 'publishing…';
+    error = '';
+    recoverable = false;
+    try {
+      const body = await apiFetch<PublishOk>(`/slabs/${slab.id}/publish`, { method: 'POST' });
+      result = body;
+      status = body.draft ? 'published as DRAFT (SLAB-UAT-* — PUBLISH-10)' : 'published';
+      dispatch('success', { id: body.woo_product_id, draft: body.draft });
+    } catch (err) {
+      recoverable = isRecoverable(err);
+      status = 'failed';
+      if (err instanceof ApiError) {
+        error = `${err.message}${err.code === 'unpublishable' && Array.isArray((err.detail as { missing?: string[] })?.missing) ? ` (missing: ${(err.detail as { missing: string[] }).missing.join(', ')})` : ''}`;
+      } else {
+        error = 'The store is unreachable — you can retry.';
+      }
+    }
+  }
+</script>
+
+<section>
+  <h2>4. Publish (PUBLISH)</h2>
+  <p>Ready set validated → SKU lookup → taxonomy refresh → PNG upload → Woo product. SLAB-UAT-* SKUs are always created as drafts (PUBLISH-10).</p>
+
+  <div class="summary">
+    <p><strong>SKU:</strong> {slab.sku} | <strong>Price:</strong> ${slab.price} | <strong>Bdft:</strong> {slab.bdft}</p>
+    <p><strong>Title:</strong> {slab.title}</p>
+    <p>Photos: {slab.photos.length}</p>
+  </div>
+
+  {#if status}
+    <p class="status" class:ok={!!result}>{status}</p>
+  {/if}
+  {#if result}
+    <p class="ok">Woo product id: {result.woo_product_id}{result.draft ? ' (draft)' : ''}</p>
+  {/if}
+  {#if error}
+    <p class="err" role="alert">{error}{recoverable ? '' : ' Retrying will not help.'}</p>
+  {/if}
+
+  <div class="actions">
+    <button on:click={() => dispatch('back')}>← Back to review</button>
+    <button on:click={attemptPublish} disabled={!!result || (status === 'failed' && !recoverable)} class="primary">
+      {result ? 'Published' : status === 'failed' ? 'Retry publish' : 'Publish to Woo'}
+    </button>
+  </div>
+</section>
+
+<style>
+  .summary { background:#1a1a1a; padding:1rem; border-radius:4px; }
+  .status { color:#0af; }
+  .status.ok { color:#0a7; }
+  .err { color:#f88; }
+  .ok { color:#0a7; }
+  .primary { background:#0a7; color:#fff; border:none; }
+  .actions { display:flex; gap:0.75rem; margin-top:1rem; }
+</style>