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>

api/src/cartsnitch_api/routes/stores.py

@@ -0,0 +1,61 @@
+"""Store routes: list stores, manage user store connections."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from cartsnitch_api.auth.dependencies import get_current_user
+from cartsnitch_api.database import get_db
+from cartsnitch_api.schemas import ConnectStoreRequest, StoreAccountResponse, StoreResponse
+from cartsnitch_api.services.stores import StoreService
+
+router = APIRouter(tags=["stores"])
+
+
+@router.get("/stores", response_model=list[StoreResponse])
+async def list_stores(db: AsyncSession = Depends(get_db)):
+    svc = StoreService(db)
+    return await svc.list_stores()
+
+
+@router.get("/me/stores", response_model=list[StoreAccountResponse])
+async def list_user_stores(
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    return await svc.list_user_stores(user_id)
+
+
+@router.post(
+    "/me/stores/{store_slug}/connect",
+    response_model=StoreAccountResponse,
+    status_code=status.HTTP_201_CREATED,
+)
+async def connect_store(
+    store_slug: str,
+    body: ConnectStoreRequest,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    try:
+        return await svc.connect_store(user_id, store_slug, body.credentials)
+    except LookupError as e:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e)) from e
+    except ValueError as e:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail=str(e)) from e
+
+
+@router.delete("/me/stores/{store_slug}", status_code=status.HTTP_204_NO_CONTENT)
+async def disconnect_store(
+    store_slug: str,
+    user_id: UUID = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    svc = StoreService(db)
+    try:
+        await svc.disconnect_store(user_id, store_slug)
+    except LookupError as e:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e)) from e