Professional patch for MikroTik User Manager batch creation.

Files included:
- usermanager.py
- main.py

What changed:
1) Separated user creation from profile activation.
2) Activation failure no longer marks successful creation as a failed create.
3) Added safer chunk tuning for 1000+ users.
4) Added final profile fixer/verification pass.
5) Added richer API summary fields:
   - created_success
   - created_failed
   - activated_success
   - activated_failed
6) Added a hard limit for synchronous real batch creation.
   Use /batch/jobs for large real batches.
7) Single-user response now includes profile_error and activation_verified.

How to apply:
- Replace app/usermanager.py with included usermanager.py
- Replace app/main.py with included main.py
- Restart the service

Recommended usage:
- Up to 100 users: /batch is fine
- 100+ users: /batch/jobs recommended
- 250+ real users: use /batch/jobs only
