chore: commit previously untracked runtime files (splits, auth, participants, shared)

src/app/api/participants/[id]/balance/route.ts

@@ -0,0 +1,32 @@
+import { NextRequest, NextResponse } from "next/server";
+import { queryRaw } from "@/lib/db";
+
+interface BalanceRow {
+  participant_id: number;
+  name: string;
+  total_owed: number;
+  transaction_count: number;
+}
+
+export async function GET(
+  _req: NextRequest,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  const { id } = await params;
+
+  const rows = await queryRaw<BalanceRow>(
+    `SELECT ts.participant_id, p.name,
+       SUM(t.amount * ts.share_percent / 100)::numeric(12,2) as total_owed,
+       COUNT(*)::int as transaction_count
+     FROM transaction_splits ts
+     JOIN transactions t ON t.id = ts.transaction_id
+     JOIN participants p ON p.id = ts.participant_id
+     WHERE ts.participant_id = $1 AND ts.settled = false
+     GROUP BY ts.participant_id, p.name`,
+    [Number(id)]
+  );
+
+  return NextResponse.json(
+    rows[0] ?? { participant_id: Number(id), total_owed: 0, transaction_count: 0 }
+  );
+}