feat: initial project setup

backend/app/routers/rankings.py

@@ -0,0 +1,36 @@
+"""Ranking endpoints – listings sorted by ELO."""
+
+from fastapi import APIRouter, Depends
+from sqlalchemy import text
+from sqlalchemy.orm import Session
+
+from app.database import get_db
+from app.queries import LISTING_SELECT, row_to_listing
+from app.schemas import RankingResponse
+
+router = APIRouter()
+
+
+@router.get("/rankings", response_model=list[RankingResponse])
+def get_rankings(
+    status: str | None = None,
+    limit: int = 100,
+    offset: int = 0,
+    db: Session = Depends(get_db),
+):
+    """Return listings ranked by ELO rating (highest first)."""
+    query = LISTING_SELECT
+    params: dict = {"limit": limit, "offset": offset}
+
+    if status and status != "all":
+        query += " WHERE l.status = :status"
+        params["status"] = status
+
+    query += " ORDER BY elo_rating DESC, l.current_price DESC LIMIT :limit OFFSET :offset"
+    result = db.execute(text(query), params)
+    listings = [row_to_listing(row) for row in result]
+
+    return [
+        RankingResponse(rank=offset + i + 1, listing=listing)
+        for i, listing in enumerate(listings)
+    ]