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/routes/shopping.py

@@ -0,0 +1,48 @@
+"""Shopping routes: optimize list, saved lists."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from httpx import HTTPStatusError, RequestError
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.schemas import OptimizeRequest, OptimizeResponse, ShoppingListResponse
+from cartsnitch_api.services.clipartist import ClipArtistClient
+
+router = APIRouter(prefix="/shopping", tags=["shopping"])
+
+
+@router.post("/optimize", response_model=OptimizeResponse)
+async def optimize_shopping(body: OptimizeRequest, user_id: UUID = Depends(get_current_user)):
+    client = ClipArtistClient()
+    try:
+        result = await client.optimize(
+            user_id=str(user_id),
+            items=[item.model_dump() for item in body.items],
+            preferred_stores=(
+                [str(s) for s in body.preferred_stores] if body.preferred_stores else None
+            ),
+        )
+        return result
+    except HTTPStatusError as e:
+        raise HTTPException(
+            status_code=e.response.status_code,
+            detail="Shopping optimization service error",
+        ) from e
+    except RequestError:
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach shopping optimization service",
+        ) from None
+
+
+@router.get("/lists", response_model=list[ShoppingListResponse])
+async def list_shopping_lists(user_id: UUID = Depends(get_current_user)):
+    client = ClipArtistClient()
+    try:
+        return await client.get_shopping_lists(str(user_id))
+    except (HTTPStatusError, RequestError):
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Unable to reach shopping service",
+        ) from None