chore: initial project setup with backend, frontend, and infrastructure

Add complete NexaPantry application structure including:
- Docker Compose configuration with PostgreSQL, Redis, FastAPI backend, worker, frontend and Caddy
- Environment configuration template with database, auth, and service settings
- GitHub Actions CI workflow for backend/frontend linting, testing, auditing and Docker builds
- AGPL-3.0 license and comprehensive README with setup, development, and security documentation
- Backend

backend/app/services/products.py

@@ -0,0 +1,51 @@
+from datetime import date
+from typing import Protocol
+
+import httpx
+from sqlalchemy.orm import Session
+
+from app.models.entities import Home, Product
+
+
+def expiry_status(product: Product, home: Home) -> str:
+    if not product.expires_at:
+        return "ok"
+    today = date.today()
+    if product.expires_at <= today:
+        return "expired"
+    if (product.expires_at - today).days <= home.expiry_warning_days:
+        return "soon"
+    return "ok"
+
+
+class ProductLookup(Protocol):
+    async def by_barcode(self, barcode: str) -> dict | None:
+        ...
+
+
+class OpenFoodFactsLookup(ProductLookup):
+    async def by_barcode(self, barcode: str) -> dict | None:
+        url = f"https://world.openfoodfacts.org/api/v2/product/{barcode}.json"
+        async with httpx.AsyncClient(timeout=8) as client:
+            response = await client.get(url)
+        if response.status_code != 200:
+            return None
+        data = response.json()
+        product = data.get("product")
+        if not product:
+            return None
+        return {
+            "name": product.get("product_name") or product.get("generic_name") or "",
+            "brand": product.get("brands"),
+            "category": (product.get("categories_tags") or ["Other"])[0].replace("en:", ""),
+            "image_url": product.get("image_front_small_url") or product.get("image_url"),
+            "barcode": barcode,
+        }
+
+
+def low_stock_products(db: Session, home_id: str) -> list[Product]:
+    return [
+        product
+        for product in db.query(Product).filter(Product.home_id == home_id).all()
+        if product.quantity <= product.min_quantity
+    ]