refactor(drivers): organize backup modules into drivers subfolder

- Move all backup_*.py files to libtisbackup/drivers/ subdirectory
- Move XenAPI.py and copy_vm_xcp.py to drivers/ (driver-specific)
- Create drivers/__init__.py with automatic driver imports
- Update tisbackup.py imports to use new structure
- Add pyvmomi>=8.0.0 as mandatory dependency
- Sync requirements.txt with pyproject.toml dependencies
- Add pylint>=3.0.0 and pytest-cov>=6.0.0 to dev dependencies
- Configure pylint and coverage tools in pyproject.toml
- Add conventional commits guidelines to CLAUDE.md
- Enhance .gitignore with comprehensive patterns for Python, IDEs, testing, and secrets
- Update CLAUDE.md documentation with new structure and tooling

Breaking Changes:
- Drivers must now be imported from libtisbackup.drivers instead of libtisbackup
- All backup driver files relocated to drivers/ subdirectory

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tisbackup_gui.py

@@ -39,7 +39,7 @@ from flask import Flask, Response, abort, appcontext_pushed, flash, g, jsonify,
 from iniparse import ConfigParser, RawConfigParser
 
 from config import huey
-from libtisbackup.common import *
+from libtisbackup import *
 from libtisbackup.auth import get_auth_provider
 from tasks import get_task, run_export_backup, set_task
 from tisbackup import tis_backup