feat(backend): add admin plugin and create-admin script (#80)

* feat(backend): add admin plugin and create-admin script

Add Better Auth admin plugin for role-based user management.
Includes a CLI script to create admin accounts.

Co-authored-by: Ona <no-reply@ona.com>

* fix(backend): guard against missing BETTER_AUTH_SECRET

Co-authored-by: Ona <no-reply@ona.com>

---------

Co-authored-by: Ona <no-reply@ona.com>

apps/aelis-backend/src/scripts/create-admin.ts

@@ -0,0 +1,63 @@
+/**
+ * Creates an admin user account via Better Auth's server-side API.
+ *
+ * Usage:
+ *   bun run src/scripts/create-admin.ts --name "Admin" --email admin@example.com --password secret123
+ *
+ * Requires DATABASE_URL and BETTER_AUTH_SECRET to be set (reads .env automatically).
+ */
+
+import { parseArgs } from "util"
+
+import { createAuth } from "../auth/index.ts"
+import { createDatabase } from "../db/index.ts"
+
+function parseCliArgs(): { name: string; email: string; password: string } {
+	const { values } = parseArgs({
+		args: Bun.argv.slice(2),
+		options: {
+			name: { type: "string" },
+			email: { type: "string" },
+			password: { type: "string" },
+		},
+		strict: true,
+	})
+
+	if (!values.name || !values.email || !values.password) {
+		console.error(
+			"Usage: bun run src/scripts/create-admin.ts --name <name> --email <email> --password <password>",
+		)
+		process.exit(1)
+	}
+
+	return { name: values.name, email: values.email, password: values.password }
+}
+
+async function main() {
+	const { name, email, password } = parseCliArgs()
+
+	const databaseUrl = process.env.DATABASE_URL
+	if (!databaseUrl) {
+		console.error("DATABASE_URL is not set")
+		process.exit(1)
+	}
+
+	const { db, close } = createDatabase(databaseUrl)
+
+	try {
+		const auth = createAuth(db)
+
+		const result = await auth.api.createUser({
+			body: { name, email, password, role: "admin" },
+		})
+
+		console.log(`Admin account created: ${result.user.id} (${result.user.email})`)
+	} finally {
+		await close()
+	}
+}
+
+main().catch((err) => {
+	console.error("Failed to create admin account:", err)
+	process.exit(1)
+})