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

web/css/copilot-input.css

@@ -6,6 +6,14 @@
   flex-shrink: 0;
 }
 
+.chat-no-models {
+  margin-bottom: 0.6rem;
+  padding: 0.7rem 0.9rem;
+  font-size: 0.82rem;
+}
+.chat-no-models .home-banner-icon { font-size: 1.2rem; }
+.chat-no-models a { color: var(--bs-danger); font-weight: 600; }
+
 .copilot-composer {
   position: relative;
   display: flex;