Initial project scaffold

Full-stack Dutch supermarket price tracker with FastAPI backend,
PostgreSQL/SQLAlchemy, Albert Heijn scraper, and Next.js frontend.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/routers/prices.py

@@ -0,0 +1,57 @@
+from datetime import date, datetime
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy import func, select
+from sqlalchemy.orm import Session, selectinload
+
+from ..database import get_db
+from ..models import PriceSnapshot, Product
+from ..schemas import CheapestProduct, Product as ProductSchema
+
+router = APIRouter(prefix="/api/prices", tags=["prices"])
+
+
+@router.get("/cheapest", response_model=list[CheapestProduct])
+def get_cheapest(
+    date_filter: date = Query(default=None, alias="date"),
+    limit: int = Query(default=20, le=100),
+    db: Session = Depends(get_db),
+):
+    target = date_filter or date.today()
+    day_start = datetime(target.year, target.month, target.day, 0, 0, 0)
+    day_end = datetime(target.year, target.month, target.day, 23, 59, 59)
+
+    min_per_product = (
+        select(
+            PriceSnapshot.product_id,
+            func.min(PriceSnapshot.price).label("min_price"),
+        )
+        .where(PriceSnapshot.timestamp.between(day_start, day_end))
+        .group_by(PriceSnapshot.product_id)
+        .subquery()
+    )
+
+    rows = db.execute(
+        select(PriceSnapshot, Product)
+        .join(
+            min_per_product,
+            (PriceSnapshot.product_id == min_per_product.c.product_id)
+            & (PriceSnapshot.price == min_per_product.c.min_price),
+        )
+        .join(Product, PriceSnapshot.product_id == Product.id)
+        .options(selectinload(Product.store))
+        .order_by(PriceSnapshot.price.asc())
+        .limit(limit)
+    ).all()
+
+    return [
+        CheapestProduct(
+            product=ProductSchema.model_validate(product),
+            price=snapshot.price,
+            unit_price=snapshot.unit_price,
+            unit_description=snapshot.unit_description,
+            is_on_sale=snapshot.is_on_sale,
+            timestamp=snapshot.timestamp,
+        )
+        for snapshot, product in rows
+    ]