feat: add canonical spot URLs

apps/api/app/main.py

@@ -135,6 +135,19 @@ def _spot_or_404(db: Session, spot_id: UUID) -> Spot:
     return spot
 
 
+@app.get("/api/v1/spots/resolve", response_model=SpotOut)
+def resolve_spot(
+    db: Db, waterbody: str, x: int = Query(ge=-10_000, le=10_000),
+    y: int = Query(ge=-10_000, le=10_000),
+) -> SpotOut:
+    spot = db.scalar(select(Spot).options(joinedload(Spot.waterbody)).join(Spot.waterbody).where(
+        Waterbody.slug == waterbody, Spot.x == x, Spot.y == y,
+    ))
+    if spot is None:
+        raise HTTPException(status_code=404, detail="spot not found")
+    return spot_detail(spot.id, db)
+
+
 @app.get("/api/v1/spots/{spot_id}", response_model=SpotOut)
 def spot_detail(spot_id: UUID, db: Db) -> SpotOut:
     spot = _spot_or_404(db, spot_id)