fix(auth): use env-configurable bcrypt rounds to prevent test timeout

HashedPassword.vo.spec.ts was timing out because SALT_ROUNDS=12 is too
expensive for the test runner. Make bcrypt rounds configurable via
BCRYPT_ROUNDS env var (default 12 for production), and set BCRYPT_ROUNDS=4
in vitest config for fast unit tests.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/vitest.config.ts

@@ -7,6 +7,9 @@ export default defineConfig({
     environment: 'node',
     include: ['src/**/*.spec.ts'],
     exclude: ['src/**/*.integration.spec.ts', 'node_modules'],
+    env: {
+      BCRYPT_ROUNDS: '4',
+    },
   },
   resolve: {
     alias: {