RK Firmware Updater 0.1.5

Major usability and safety update for RK Firmware Updater.\n\nHighlights:\n- New Betaflight-style left navigation with Flash and Parameters tabs.\n- New Parameters view with full JSON configuration editor.\n- Load external configuration JSON, export the current JSON, apply changes, and reset to packaged defaults.\n- Improved global progress handling: online loader/image workflows now map download and flash phases across the full progress bar.\n- Simulation mode now uses the same global progress mapping as real flashing.\n- Reboot behavior is safer and only blocked during actual flash commands.\n- Downloads and flash failures now stop the workflow immediately with clearer user-facing errors.\n- Added rollback tests for interrupted network downloads so partial update files are not kept.\n- Additional tests for Parameters actions, failure handling, and UI layout.\n\nArtifacts for macOS, Windows, and Linux are uploaded automatically by GitHub Actions after the release workflows complete.