Add a foreign key constraint to link invoices to specific jobs

Adds a foreign key constraint to the `invoices` table, referencing the `id` column in the `jobs` table, ensuring data integrity.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 418bf6f8-212b-4bb0-a7a5-8231a061da4e
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: d9dd1cc2-bc61-41c5-90bb-94504f4308a9
Replit-Helium-Checkpoint-Created: true

lib/db/src/schema/invoices.ts

@@ -1,13 +1,14 @@
 import { pgTable, text, integer, boolean, timestamp } from "drizzle-orm/pg-core";
 import { createInsertSchema } from "drizzle-zod";
 import { z } from "zod/v4";
+import { jobs } from "./jobs";
 
 export const INVOICE_TYPES = ["eval", "work"] as const;
 export type InvoiceType = (typeof INVOICE_TYPES)[number];
 
 export const invoices = pgTable("invoices", {
   id: text("id").primaryKey(),
-  jobId: text("job_id").notNull(),
+  jobId: text("job_id").notNull().references(() => jobs.id),
   paymentHash: text("payment_hash").notNull().unique(),
   paymentRequest: text("payment_request").notNull(),
   amountSats: integer("amount_sats").notNull(),