Add config.min_version for version gating

[ericof]

Summary

• Template repositories can now declare config.min_version in cookieplone-config.json. When the installed Cookieplone is older than the required version, generation stops early with a clear upgrade instruction.
• Added VersionTooOldException and wired it through the CLI error handling.
• Updated the JSON schema to accept the new min_version field.
• Welcome screen now displays the installed Cookieplone version in the panel title.
• Added docstrings and type annotations to all functions in console.py.

Closes #180

Test plan

• pytest passes (895 tests, 10 new for min_version)
• ruff check and ruff format clean
• vale passes with 0 errors
• Pre-commit hooks pass
• Verify version satisfied, version too old, missing key, pre-release, and dev version scenarios
• Verify welcome screen shows version in panel title