feat: initial finance SPA — phases 1 & 2

Next.js 16 personal finance dashboard connected to postgres-personal.

Phase 1 (Foundation):
- API routes: GET /api/transactions (paginated, filterable, sortable),
  GET /api/statements, GET /api/merchants
- Transactions data table with date/category/bank/search filters, pagination, sort
- Statements card grid with period, due date, amount, transaction count
- Sidebar layout with nav for all planned sections

Phase 2 (Normalisation):
- PATCH /api/transactions/[id] — upsert transaction_overrides
- POST /api/transactions/bulk — bulk categorize/normalize
- Inline click-to-edit category (22 options) and merchant name
- Blue dot override indicator, bulk action bar
- Effective values via COALESCE(override, llm_value) pattern

Stack: Next.js 16 (App Router, standalone), Prisma 7.x + @prisma/adapter-pg,
TanStack Query, Tailwind CSS. Auth via Traefik chain-oauth@file.

src/lib/db.ts

@@ -0,0 +1,17 @@
+import { PrismaClient } from "@/generated/prisma/client";
+import { PrismaPg } from "@prisma/adapter-pg";
+
+const globalForPrisma = globalThis as unknown as { prisma: PrismaClient };
+
+function createPrisma() {
+  const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL! });
+  return new PrismaClient({ adapter });
+}
+
+export const prisma = globalForPrisma.prisma || createPrisma();
+
+if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;
+
+export async function queryRaw<T>(sql: string, params: unknown[] = []): Promise<T[]> {
+  return prisma.$queryRawUnsafe<T[]>(sql, ...params);
+}