security: remove hardcoded DB credentials from code files

prisma/seed.ts

@@ -2,9 +2,11 @@ import { Pool } from 'pg';
 import { PrismaPg } from '@prisma/adapter-pg';
 import { PrismaClient } from '@prisma/client';
 
-const connectionString =
-  process.env.DATABASE_URL ||
-  'postgres://postgres:mBTWE2cDKGExtpktguD3HPe8y9Xr9kWFYdxV4WHQKISLLGoBAS4UdtfSCfXwvPpq@65.109.236.58:37298/postgres';
+const connectionString = process.env.DATABASE_URL;
+
+if (!connectionString) {
+  throw new Error('[Seed] DATABASE_URL environment variable is not set!');
+}
 
 const pool = new Pool({ connectionString });
 const adapter = new PrismaPg(pool);
@@ -20,6 +22,7 @@ async function main() {
   await db.lesson.deleteMany();
   await db.cheatsheetItem.deleteMany();
   await db.cheatsheet.deleteMany();
+  await db.prompt.deleteMany();
 
   // Create Lessons
   await db.lesson.create({
@@ -93,13 +96,12 @@ async function main() {
   });
 
   // Create Prompts
-  await db.prompt.deleteMany();
   await db.prompt.create({
     data: {
       slug: 'fullstack-nextjs-architect-prompt',
       title: 'Full-Stack Next.js 16 System Architect Prompt',
       category: 'System Architecture',
-      description: 'System prompt for building production-ready Next.js 16 App Router code with Server Actions and Prisma.',
+      description: 'System prompt for building production-ready Next.js 16 App Router code.',
       content: `You are a Senior Next.js 16 Architect. Always use TypeScript strict mode, App Router, proxy.ts for middleware, Server Actions with Zod validation, and Prisma ORM.`,
       tags: ['Next.js', 'System Prompt', 'AI Architecture'],
       isOpen: false,