fix(minio): support mc_path and harden sync against transient objects

src/config/schema.test.ts

@@ -284,6 +284,7 @@ describe('configSchema — backup', () => {
     expect(result.backup.minio.enabled).toBe(false);
     expect(result.backup.minio.prefix).toBe('flynn');
     expect(result.backup.minio.secure).toBe(true);
+    expect(result.backup.minio.mc_path).toBeUndefined();
   });
 
   it('accepts custom backup settings', () => {
@@ -307,6 +308,7 @@ describe('configSchema — backup', () => {
           bucket: 'flynn-backups',
           prefix: 'daily',
           secure: false,
+          mc_path: '/usr/local/bin/mc',
         },
       },
     });
@@ -325,6 +327,7 @@ describe('configSchema — backup', () => {
     expect(result.backup.minio.bucket).toBe('flynn-backups');
     expect(result.backup.minio.prefix).toBe('daily');
     expect(result.backup.minio.secure).toBe(false);
+    expect(result.backup.minio.mc_path).toBe('/usr/local/bin/mc');
   });
 });