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>

src/cartsnitch_api/services/clipartist.py

@@ -0,0 +1,52 @@
+"""HTTP client for ClipArtist internal API."""
+
+from typing import Any, cast
+
+import httpx
+
+from cartsnitch_api.config import settings
+
+
+class ClipArtistClient:
+    def __init__(self) -> None:
+        self.base_url = settings.clipartist_url
+        self.headers = {"X-Service-Key": settings.service_key}
+
+    async def optimize(
+        self,
+        user_id: str,
+        items: list[dict],
+        preferred_stores: list[str] | None = None,
+    ) -> dict:
+        async with httpx.AsyncClient() as client:
+            resp = await client.post(
+                f"{self.base_url}/optimize",
+                headers=self.headers,
+                json={
+                    "user_id": user_id,
+                    "items": items,
+                    "preferred_stores": preferred_stores,
+                },
+            )
+            resp.raise_for_status()
+            return cast(dict[str, Any], resp.json())
+
+    async def get_shopping_lists(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/shopping-lists",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())
+
+    async def get_relevant_coupons(self, user_id: str) -> list[dict]:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                f"{self.base_url}/coupons/relevant",
+                headers=self.headers,
+                params={"user_id": user_id},
+            )
+            resp.raise_for_status()
+            return cast(list[dict[str, Any]], resp.json())