docs: add OSS project docs and CI

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project are documented here.
+
+The format follows the spirit of [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project is licensed under GNU GPL v3.0 or later.
+
+## Unreleased
+
+### Added
+
+- Human-first Russian and English README files.
+- Security, contributing, vendored dependency and authorship documentation.
+- Example `secrets.env.example` for safe setup.
+- Root GitHub Actions CI workflow for tests, linting, packaging checks and Docker build.
+
+### Changed
+
+- Root project metadata is now described in `pyproject.toml`.
+- Ruff configuration covers a broader set of checks while allowing intentional Cyrillic UI text.
+
+### Security
+
+- Documented secret storage, token rotation and Telegram CSV export privacy expectations.