Use explicit ubuntu:22.04 container instead of marketplace actions
that may not work on self-hosted Gitea runners. Install Node.js and
Rust toolchain directly via curl/rustup.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adapt GitHub Actions workflows for Gitea with Docker runner:
- Linux-only builds (no macOS/Windows matrix)
- Manual `npm run tauri build` instead of tauri-action
- Release creation via Gitea API with asset upload
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>