feat: receive and serve product images pushed from local sites

New POST /api/menu/sync-image (site-authenticated) accepts a product's
image file, stores it under /app/data/product_images keyed by
(site, product_id), and skips the write entirely if the uploaded
content hash matches what's already stored. GET /api/menu/{site_slug}
now injects the cloud-hosted image URL into each product that has no
manual digital_image_url override — replacing the local-only image_url
from the snapshot, which was never reachable from the public internet.

Also fixes the menu-app resolving product image URLs as bare relative
paths instead of prefixing them with the cloud API origin (same class
of bug as the earlier header-image fix).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

cloud_backend/routers/menu.py

@@ -1,15 +1,20 @@
-from fastapi import APIRouter, Depends, HTTPException, Header, status
+import os
+import uuid
+from fastapi import APIRouter, Depends, HTTPException, Header, UploadFile, File, Form, status
 from passlib.context import CryptContext
 from sqlalchemy.orm import Session
 
 from database import get_db
 from models.site import Site
 from models.menu_snapshot import MenuSnapshot
+from models.product_image import ProductImage
 from schemas.menu import MenuSyncRequest, MenuSyncResponse
 
 router = APIRouter()
 _pwd = CryptContext(schemes=["bcrypt"], deprecated="auto")
 
+PRODUCT_IMAGE_DIR = "/app/data/product_images"
+
 
 def _require_site(
     x_site_id: str = Header(..., alias="X-Site-ID"),
@@ -45,6 +50,20 @@ def get_menu(site_slug: str, db: Session = Depends(get_db)):
         "hours": site.menu_hours,
         "headerImageUrl": site.menu_header_image_url,
     }
+
+    cloud_images = {
+        img.product_id: img.image_url
+        for img in db.query(ProductImage).filter(ProductImage.site_id == site.id).all()
+    }
+    for cat in data.get("categories", []):
+        for product in cat.get("products", []):
+            # image_url as pushed by local_backend points at the restaurant's own
+            # LAN/local server and isn't reachable from the internet — always
+            # replace it with the cloud-hosted copy (or None) unless a manual
+            # digital_image_url override is set.
+            if not product.get("digital_image_url"):
+                product["image_url"] = cloud_images.get(product.get("id"))
+
     return data
 
 
@@ -61,3 +80,54 @@ def sync_menu(body: MenuSyncRequest, site: Site = Depends(_require_site), db: Se
         db.add(snapshot)
     db.commit()
     return MenuSyncResponse(ok=True)
+
+
+@router.post("/sync-image")
+async def sync_product_image(
+    product_id: int = Form(...),
+    file: UploadFile = File(...),
+    site: Site = Depends(_require_site),
+    db: Session = Depends(get_db),
+):
+    """Upload/replace the cloud-hosted copy of a product's image. Called by
+    local_backend during menu sync for products whose image changed."""
+    if not file.content_type or not file.content_type.startswith("image/"):
+        raise HTTPException(status_code=400, detail="File must be an image")
+
+    contents = await file.read()
+
+    import hashlib
+    image_hash = hashlib.sha256(contents).hexdigest()
+
+    record = (
+        db.query(ProductImage)
+        .filter(ProductImage.site_id == site.id, ProductImage.product_id == product_id)
+        .first()
+    )
+
+    os.makedirs(PRODUCT_IMAGE_DIR, exist_ok=True)
+
+    if record and record.image_hash == image_hash:
+        return {"ok": True, "image_url": record.image_url, "unchanged": True}
+
+    if record:
+        old_path = os.path.join(PRODUCT_IMAGE_DIR, os.path.basename(record.image_url))
+        if os.path.exists(old_path):
+            os.remove(old_path)
+
+    ext = file.filename.rsplit(".", 1)[-1].lower() if file.filename and "." in file.filename else "jpg"
+    filename = f"{site.id}_{product_id}_{uuid.uuid4().hex[:8]}.{ext}"
+    filepath = os.path.join(PRODUCT_IMAGE_DIR, filename)
+    with open(filepath, "wb") as f:
+        f.write(contents)
+
+    image_url = f"/static/product_images/{filename}"
+    if record:
+        record.image_url = image_url
+        record.image_hash = image_hash
+    else:
+        record = ProductImage(site_id=site.id, product_id=product_id, image_url=image_url, image_hash=image_hash)
+        db.add(record)
+    db.commit()
+
+    return {"ok": True, "image_url": image_url, "unchanged": False}