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>

libtisbackup/__init__.py

@@ -15,3 +15,77 @@
 #    along with TISBackup.  If not, see <http://www.gnu.org/licenses/>.
 #
 # -----------------------------------------------------------------------
+
+"""
+TISBackup library - Backup orchestration and driver management.
+
+This package provides a modular backup system with:
+- Base driver classes for implementing backup types
+- Database management for backup statistics
+- SSH and process execution utilities
+- Date/time and formatting helpers
+"""
+
+# Import from new modular structure
+from .base_driver import (
+    backup_drivers,
+    backup_generic,
+    nagiosStateCritical,
+    nagiosStateOk,
+    nagiosStateUnknown,
+    nagiosStateWarning,
+    register_driver,
+)
+from .database import BackupStat
+from .process import call_external_process, monitor_stdout
+from .ssh import load_ssh_private_key, ssh_exec
+from .utils import (
+    check_string,
+    convert_bytes,
+    dateof,
+    datetime2isodate,
+    fileisodate,
+    hours_minutes,
+    html_table,
+    isodate2datetime,
+    pp,
+    splitThousands,
+    str2bool,
+    time2display,
+)
+
+# Maintain backward compatibility - re-export everything that was in common.py
+__all__ = [
+    # Nagios states
+    "nagiosStateOk",
+    "nagiosStateWarning",
+    "nagiosStateCritical",
+    "nagiosStateUnknown",
+    # Driver registry
+    "backup_drivers",
+    "register_driver",
+    # Base classes
+    "backup_generic",
+    "BackupStat",
+    # SSH utilities
+    "load_ssh_private_key",
+    "ssh_exec",
+    # Process utilities
+    "call_external_process",
+    "monitor_stdout",
+    # Date/time utilities
+    "datetime2isodate",
+    "isodate2datetime",
+    "time2display",
+    "hours_minutes",
+    "fileisodate",
+    "dateof",
+    # Formatting utilities
+    "splitThousands",
+    "convert_bytes",
+    "pp",
+    "html_table",
+    # Validation utilities
+    "check_string",
+    "str2bool",
+]