feat(trips): trip tracking with analytics, tag conversion, and transaction assignment

Adds trips table usage across API and UI: trip CRUD, per-trip analytics
(category/daily/merchant/tag/participant breakdowns), tag-to-trip
conversion, trip assignment via transaction overrides, and trip filter
in the transactions view. Recovered from working tree after local git
corruption; feature was already live via host-context Docker builds.

src/app/api/trips/route.ts

@@ -0,0 +1,20 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getCurrentUser } from "@/lib/auth";
+import { getTrips, createTrip } from "@/lib/queries";
+
+export async function GET(req: NextRequest) {
+  const user = await getCurrentUser(req);
+  if (!user) return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  const trips = await getTrips(user.id);
+  return NextResponse.json(trips);
+}
+
+export async function POST(req: NextRequest) {
+  const user = await getCurrentUser(req);
+  if (!user) return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  const body = await req.json();
+  const { name, description, start_date, end_date, color } = body;
+  if (!name?.trim()) return NextResponse.json({ error: "name is required" }, { status: 400 });
+  const trip = await createTrip(user.id, { name: name.trim(), description, start_date, end_date, color });
+  return NextResponse.json(trip, { status: 201 });
+}