docs: percantik halaman repo — badge lengkap + diagram alur di README, template issue laporan hardware, CONTRIBUTING, SECURITY, dan kartu social preview

CONTRIBUTING.md

@@ -0,0 +1,33 @@
+# Contributing
+
+Thanks for helping — the most valuable contribution is **hardware reports**: which cooler
+works, which firmware revision differs, which sensor channel has to be picked. Use the
+*Hardware report* issue template, or send a pull request.
+
+## Before opening a pull request
+
+The sender must stay dependency-free (standard library only) and must never write to the
+device unless the user asked for it.
+
+```bash
+# nothing is written to the panel:
+python3 src/gamemax_report.py --dry-run
+python3 src/gamemax_report.py --list-sensors
+
+# the tray app self-checks without a display, and can exercise every action:
+uv run --with pyside6 python src/gamemax_gui.py --selftest
+uv run --with pyside6 python src/gamemax_gui.py --selftest-actions
+
+# build the AppImage (needs uv + network on first run):
+bash packaging/build_appimage.sh
+```
+
+`--selftest-actions` really does start/stop the service and toggle autostart, then leaves
+the service running — expected.
+
+## Style
+
+- Python 3.10+, no new dependencies, comments only where the code cannot explain itself.
+- GUI strings are Indonesian (the original author's language); code and docs are English.
+- Keep the protocol knowledge in `docs/reverse-engineering.md` and the README table in sync
+  when you learn something new about the panel.