Implement P1 local matcher/ledger and P2 strategy engine.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/api/trades.py

@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+from typing import Annotated, Any
+
+from fastapi import APIRouter, Depends, HTTPException
+
+from ..models.db import get_db
+from .auth import require_user
+
+router = APIRouter(prefix="/api/trades", tags=["trades"])
+
+
+def _row(r: Any) -> dict:
+    return dict(r)
+
+
+@router.get("/groups")
+async def list_groups(_user: Annotated[str, Depends(require_user)]) -> dict:
+    rows = get_db().fetchall(
+        "SELECT * FROM groups ORDER BY open_at_ms DESC LIMIT 200"
+    )
+    return {"groups": [_row(x) for x in rows]}
+
+
+@router.get("/groups/{group_id}")
+async def group_detail(group_id: str, _user: Annotated[str, Depends(require_user)]) -> dict:
+    db = get_db()
+    g = db.fetchone("SELECT * FROM groups WHERE group_id=?", (group_id,))
+    if g is None:
+        raise HTTPException(status_code=404, detail="group not found")
+    fills = db.fetchall(
+        "SELECT * FROM fills WHERE group_id=? ORDER BY id ASC", (group_id,)
+    )
+    return {"group": _row(g), "fills": [_row(x) for x in fills]}