10refactor(storage): reduce HetznerStorageClient wrapper duplication

Refactoring Request Template

Title (semantic)
refactor(storage): reduce HetznerStorageClient wrapper duplication

Description
This merge request refactors app/utils/hetzner_storage.py to reduce duplicated wrapper logic around the MinIO SDK and simplify the Hetzner storage client implementation.

Refactor highlights:

• Audited methods inside HetznerStorageClient
• Removed direct SDK passthrough wrappers
• Simplified presigned URL handling using MinIO SDK delegation
• Simplified upload progress tracking implementation
• Removed dead code and unused imports
• Preserved business logic including validation, logging, formatting, and object key generation
• Reduced maintenance surface and wrapper complexity
• Improved readability and maintainability while preserving existing behavior

Checklist

• Code has been refactored for clarity, maintainability, or performance
  • No functional changes have been introduced
  • All existing tests are passing
  • Code adheres to project coding standards

Related Issue(s)
Closes #104