Prepare project for public release

CONTRIBUTING.md

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+# Contributing
+
+Thanks for helping improve WLC Monitor.
+
+## Before you start
+
+Use GitHub Issues for reproducible bugs and focused feature proposals. Search
+existing issues first. Use the private process in [SECURITY.md](SECURITY.md)
+for vulnerabilities.
+
+## Development setup
+
+```bash
+python3 -m venv .venv
+. .venv/bin/activate
+python -m pip install -r requirements.txt
+cp config.ini.example config.ini
+chmod 600 config.ini
+```
+
+Never commit real credentials or infrastructure data. Use reserved example
+addresses/domains and synthetic state fixtures.
+
+## Making changes
+
+- Create a focused branch.
+- Add or update tests for behavior changes.
+- Update the README and configuration examples for user-visible changes.
+- Keep unrelated formatting out of the patch.
+
+Run the local checks before opening a pull request:
+
+```bash
+python -m py_compile wlc_monitor.py
+python -m unittest discover -v
+python -m pip check
+```
+
+If Docker is available, also run:
+
+```bash
+cp .env.example .env
+docker compose config --quiet
+docker build -t wlc-monitor:test .
+```
+
+Remove the local `.env` afterward or keep it private; it is ignored by Git.
+
+## Pull requests
+
+Explain the problem and solution, link related issues, list the checks you ran,
+and call out compatibility or operational impact. Confirm that the diff
+contains no credentials, `.env`, `config.ini`, `state.json`, controller/AP
+identifiers, or personal data.