docs: Add version support policy and changelog

- Establish formal version maintenance strategy
- Define BIND9 9.18 (LTS) and 9.20+ support tiers
- Document branching strategy (main for 9.18, 9.20 for next major)
- Define backporting policies for security, bugs, features
- Create release management and CI/CD framework
- Add OS platform compatibility matrix

CHANGELOG.md

@@ -0,0 +1,114 @@
+# Changelog
+
+All notable changes to the ansible-bind9-role will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- Version support policy documentation in `docs/VERSION_SUPPORT.md`
+- Branching strategy for supporting multiple BIND9 versions
+- Grammar comparison tooling (`scripts/compare_bind_versions.py`)
+- Grammar fetcher for upstream BIND9 sources (`scripts/fetch_bind_grammar.py`)
+- Automated version difference tracking
+- Operating system support matrix
+
+### Changed
+- Established formal release management process
+- Defined backporting policy for security, bugs, and features
+
+### Planned
+- BIND9 9.20+ support in separate `9.20` branch
+- Multi-platform molecule test matrix
+- Automated BIND9 version detection in tasks
+- Version-specific template conditional logic
+- Enhanced CI/CD pipeline with version matrix testing
+
+## [1.0.0] - TBD
+
+### Initial Release
+- Full support for BIND9 9.18.x (LTS)
+- Configuration grammar based on BIND9 9.18.44
+- Comprehensive template system for all BIND9 statement types:
+  - `acl`
+  - `controls`
+  - `dlz`
+  - `dnssec-policy`
+  - `dyndb`
+  - `http`
+  - `key`
+  - `logging`
+  - `options`
+  - `parental-agents`
+  - `primaries` (masters)
+  - `server`
+  - `statistics-channels`
+  - `tls`
+  - `trust-anchors`
+  - `view`
+  - `zone` (all types: primary, secondary, forward, hint, stub, static-stub, mirror, redirect, in-view, delegation-only)
+- Support for Debian 11, 12, 13
+- Support for Ubuntu 20.04, 22.04, 24.04
+- Molecule testing framework
+- Configuration validation with `named-checkconf`
+- Automatic configuration backup and rollback on errors
+- Detailed configuration grammar documentation
+- GPL-3.0-or-later license
+
+---
+
+## Version History (Pre-Changelog)
+
+Prior to this changelog, the role was developed without formal version tracking. 
+This changelog starts with the establishment of the version support policy.
+
+---
+
+## Versioning Schema
+
+- **MAJOR**: Incompatible changes to role variables or behavior
+- **MINOR**: New features in a backwards compatible manner
+- **PATCH**: Backwards compatible bug fixes
+
+### Branch-Specific Versioning
+
+- `main` branch: `vX.Y.Z` (BIND9 9.18 LTS)
+- `9.20` branch: `v9.20.X[-suffix]` (BIND9 9.20+)
+  - Suffixes: `-alpha`, `-beta`, `-rc` for pre-releases
+
+## Release Types
+
+### Security Releases
+Critical security fixes are released as patch versions and backported to all supported branches.
+
+### Feature Releases
+New features are added in minor version increments. Breaking changes require major version increments.
+
+### Bug Fix Releases
+Bug fixes are released as patch versions when they accumulate or for critical issues.
+
+## Upgrade Notes
+
+### From Pre-Versioned to v1.0.0
+The first official release establishes baseline compatibility. Users of pre-release versions should:
+1. Review all role variables for any changes
+2. Test in non-production environment
+3. Review generated configuration with `named-checkconf`
+4. Check `docs/VERSION_SUPPORT.md` for supported platforms
+
+### Future Upgrades
+Check individual version sections above for specific upgrade notes and breaking changes.
+
+## Contributing
+
+See `docs/VERSION_SUPPORT.md` for contribution guidelines and release processes.
+
+## Links
+
+- [Version Support Policy](docs/VERSION_SUPPORT.md)
+- [Configuration Grammar](CONFIGURATION_GRAMMAR.md)
+- [Issue Tracker](https://git.valid.dk/daniel/ansible-bind9-role/issues)
+- [Repository](https://git.valid.dk/daniel/ansible-bind9-role)
+