Fix product preorder and warranty submit flow

HANDOFF.md

@@ -22,6 +22,41 @@ npx tsc --noEmit
 
 ## Latest Codex Changes After `76fb4f3`
 
+### Product create preorder and warranty submit rules
+
+Files:
+- `src/app/(dashboard)/products/new/details/page.tsx`
+- `src/app/(dashboard)/products/new/specifications/page.tsx`
+- `src/app/(dashboard)/products/new/review/page.tsx`
+- `src/lib/product-draft.tsx`
+- `src/lib/use-product-submit.ts`
+- `src/lib/product-request-validation.ts`
+
+Behavior:
+- Pre-order day placeholder is now `0`, not `14`, so an empty/unfilled value is visually obvious.
+- If pre-order is checked, the Details step blocks Next unless `preOrderDay` is a valid number greater than or equal to 1.
+- Warranty now has an On/Off switch in the Specifications step.
+- When warranty is On:
+  - warranty type is required
+  - warranty duration must be greater than or equal to 1
+  - the review page shows warranty information
+  - submit payload sends the filled `warrantyInformation` object
+- When warranty is Off:
+  - warranty inputs are disabled and dimmed
+  - the review page hides warranty information
+  - submit payload still sends `warrantyInformation` as an object required by the backend, with:
+
+```json
+{
+  "type": null,
+  "duration": null,
+  "durationType": "MONTH"
+}
+```
+
+- Frontend payload validation treats the above null-valued warranty object as warranty Off, so it does not block submit with warranty type/duration errors.
+- Local test server was rebuilt and restarted against `https://api-dev.inatrading.co.id` in `.env.local`; `.env.local` is not committed.
+
 ### AddProductRequest validation
 
 Files: