feat: add PostgreSQL database adapter support

src/lib/auth.ts

@@ -3,9 +3,12 @@ import { prismaAdapter } from "better-auth/adapters/prisma";
 import { prisma } from "./prisma";
 import { testUtils } from "better-auth/plugins";
 
+// Detect database provider from environment
+const databaseProvider = process.env.DATABASE_PROVIDER || "sqlite";
+
 export const auth = betterAuth({
   database: prismaAdapter(prisma, {
-    provider: "sqlite",
+    provider: databaseProvider as "sqlite" | "postgresql",
   }),
   emailAndPassword: {
     enabled: true,