feat: migrate to Better Auth for authentication, update environment variables, and enhance database schema with accounts and sessions

Backend/auth.ts

@@ -0,0 +1,32 @@
+import { betterAuth } from 'better-auth';
+import { drizzleAdapter } from 'better-auth/adapters/drizzle';
+
+import { db } from './db/client';
+import { schema } from './db/schema';
+import { hashPassword, verifyPassword } from './utils/password';
+
+const trustedOrigins = process.env.BETTER_AUTH_TRUSTED_ORIGINS
+  ? process.env.BETTER_AUTH_TRUSTED_ORIGINS.split(',').map((origin) => origin.trim()).filter(Boolean)
+  : undefined;
+
+export const auth = betterAuth({
+  database: drizzleAdapter(db, {
+    provider: 'pg',
+    schema: {
+      ...schema,
+      user: schema.users,
+    },
+  }),
+  emailAndPassword: {
+    enabled: true,
+    password: {
+      hash: async (password) => hashPassword(password),
+      verify: async ({ hash, password }) => verifyPassword(password, hash),
+    },
+  },
+  secret: process.env.BETTER_AUTH_SECRET,
+  baseURL: process.env.BETTER_AUTH_URL,
+  trustedOrigins,
+});
+
+export type AuthSession = Awaited<ReturnType<typeof auth.api.getSession>>;