Refactor: remove desktop/Tauri bundle, add i18n, CI/CD pipeline

- Remove desktop (Tauri) bundle: docs/desktop.md, icons/, tauri.conf.json,
  src/desktop/mod.rs, gen/schemas/
- Remove build.rs (no longer needed)
- Add i18n system (crates/core-api, plugin-mobile-connector, web)
- Refactor config system (src/config.rs, boot_format.rs)
- Add mobile connector features (app, router, device pairing)
- Plugin system improvements (skald-core)
- Update dependencies (Cargo.lock, Cargo.toml)
- CI/CD: Gitea Actions workflows (nightly + release), package.sh,
  verify-version.sh, builds.skaldagent.net config

src/frontend/api/marketplace.rs

@@ -48,7 +48,7 @@ use super::ApiError;
 static FEED_URL: std::sync::OnceLock<String> = std::sync::OnceLock::new();
 
 /// Installs the feed URL from config. Called once during frontend construction;
-/// later calls are ignored, so tests and the desktop shell cannot race it.
+/// later calls are ignored, so concurrent callers (e.g. tests) cannot race it.
 pub fn set_feed_url(url: String) {
     let _ = FEED_URL.set(url.trim_end_matches('/').to_string());
 }