fix: add defensive checks to prisma.ts to prevent build failures

src/lib/prisma.ts

@@ -1,8 +1,7 @@
 import { PrismaClient } from '@prisma/client'
-import dotenv from 'dotenv'
 
 // Load .env file if it exists
-dotenv.config()
+require('dotenv').config()
 
 const globalForPrisma = globalThis as unknown as {
   prisma: PrismaClient | undefined
@@ -10,16 +9,24 @@ const globalForPrisma = globalThis as unknown as {
 
 // Detect database provider from environment (default to sqlite for local development)
 const databaseProvider = process.env.DATABASE_PROVIDER || 'sqlite'
+const databaseUrl = process.env.DATABASE_URL
 
 // Create PrismaClient with appropriate adapter
 const createPrismaClient = () => {
   let client: PrismaClient
   
   if (databaseProvider === 'postgresql') {
+    // Validate DATABASE_URL is present for PostgreSQL
+    if (!databaseUrl) {
+      throw new Error(
+        'DATABASE_URL environment variable is required when DATABASE_PROVIDER is set to postgresql. ' +
+        'Current DATABASE_PROVIDER: ' + databaseProvider
+      )
+    }
+    
     // Use PrismaPg adapter for PostgreSQL
     const { PrismaPg } = require('@prisma/adapter-pg')
-    const pg = require('pg')
-    const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL })
+    const adapter = new PrismaPg({ connectionString: databaseUrl })
     client = new PrismaClient({ adapter })
   } else {
     // No adapter needed for SQLite