refactor(env): centralize auth env handling and prefer BETTER_AUTH_BASE_URL

Backend/utils/env.ts

@@ -0,0 +1,34 @@
+const getEnvValue = (name: string): string | undefined => {
+  const value = process.env[name];
+  if (!value) {
+    return undefined;
+  }
+
+  const trimmed = value.trim();
+  return trimmed.length > 0 ? trimmed : undefined;
+};
+
+export const getFirstDefinedEnv = (...names: string[]): string | undefined => {
+  for (const name of names) {
+    const value = getEnvValue(name);
+    if (value) {
+      return value;
+    }
+  }
+
+  return undefined;
+};
+
+export const getRequiredEnv = (name: string): string => {
+  const value = getEnvValue(name);
+
+  if (!value) {
+    throw new Error(`${name} is required. Add it to your .env file.`);
+  }
+
+  return value;
+};
+
+export const getBetterAuthBaseUrl = (): string => {
+  return getFirstDefinedEnv('BETTER_AUTH_BASE_URL', 'BETTER_AUTH_URL') ?? `http://localhost:${process.env.PORT ?? '3000'}`;
+};