feat: merge cartsnitch/api into api/ subdirectory

Consolidate API gateway service into monorepo.
Squashed from https://github.com/cartsnitch/api main (89bacb1).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/test_e2e/test_product_search_lookup.py

@@ -0,0 +1,82 @@
+"""E2E: Product search/lookup endpoints with real DB fixtures."""
+
+import pytest
+
+from tests.test_e2e.conftest import ZERO_UUID
+
+
+@pytest.mark.asyncio
+class TestProductSearch:
+    """Search and filter products against seeded data."""
+
+    async def test_list_all_products(self, client, seed_data):
+        resp = await client.get("/products", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        products = resp.json()
+        names = [p["name"] for p in products]
+        assert "Cheerios 18oz" in names
+        assert "Whole Milk 1gal" in names
+        assert "Chicken Breast 1lb" in names
+
+    async def test_search_by_name(self, client, seed_data):
+        resp = await client.get("/products", params={"q": "cheerios"}, headers=seed_data["headers"])
+        assert resp.status_code == 200
+        products = resp.json()
+        assert len(products) >= 1
+        assert all("cheerios" in p["name"].lower() for p in products)
+
+    async def test_search_by_category(self, client, seed_data):
+        resp = await client.get(
+            "/products", params={"category": "dairy"}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        products = resp.json()
+        assert len(products) >= 1
+        assert all(p["category"] == "dairy" for p in products)
+
+    async def test_search_no_results(self, client, seed_data):
+        resp = await client.get(
+            "/products", params={"q": "nonexistentxyz"}, headers=seed_data["headers"]
+        )
+        assert resp.status_code == 200
+        assert resp.json() == []
+
+
+@pytest.mark.asyncio
+class TestProductLookup:
+    """Detailed product lookups with cross-store pricing."""
+
+    async def test_get_product_detail_with_prices(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["name"] == "Cheerios 18oz"
+        assert data["brand"] == "General Mills"
+        assert data["category"] == "pantry"
+        # Should have prices from both Meijer and Kroger
+        store_names = [p["store_name"] for p in data["prices_by_store"]]
+        assert "Meijer" in store_names
+        assert "Kroger" in store_names
+
+    async def test_product_prices_reflect_latest(self, client, seed_data):
+        """The latest Meijer price for Cheerios should be 4.79 (the increase)."""
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}", headers=seed_data["headers"])
+        data = resp.json()
+        meijer_price = next(p for p in data["prices_by_store"] if p["store_name"] == "Meijer")
+        assert meijer_price["current_price"] == 4.79
+
+    async def test_product_not_found(self, client, seed_data):
+        resp = await client.get(f"/products/{ZERO_UUID}", headers=seed_data["headers"])
+        assert resp.status_code == 404
+
+    async def test_product_price_history(self, client, seed_data):
+        cheerios_id = str(seed_data["products"]["cheerios"].id)
+        resp = await client.get(f"/products/{cheerios_id}/prices", headers=seed_data["headers"])
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data["data_points"]) >= 3  # At least the 3 Meijer observations
+        # Verify chronological ordering exists
+        prices = [dp["price"] for dp in data["data_points"]]
+        assert len(prices) >= 3