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/transactions/route.ts

@@ -25,6 +25,7 @@ export async function GET(req: NextRequest) {
     amount_min: sp.get("amount_min") ? Number(sp.get("amount_min")) : undefined,
     amount_max: sp.get("amount_max") ? Number(sp.get("amount_max")) : undefined,
     has_split: sp.get("has_split") || undefined,
+    trip_id: sp.get("trip_id") || undefined,
   });
 
   return NextResponse.json(result);