LLeMbas Desktop: the server in a window, the CLI's agent on this computer

Tauri 2, no Node. A first-run page chooses the server; then the window is
the server's web UI, whose pages get no IPC. The bundled LLeMbas CLI
(fetched and signature-checked by scripts/fetch-cli.sh) links the computer
with 'lembas login --json' and runs as 'lembas service' while the app runs.
A tray menu starts and stops it. Linux packages from GitHub Actions on a tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,17 @@
+# Changelog
+
+All notable changes to LLeMbas Desktop. The format follows
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and the project uses
+[Semantic Versioning](https://semver.org/).
+
+## [Unreleased]
+
+### Added
+
+- The app: the server's web UI in a window of its own, a first-run page to choose the server, and a
+  tray menu (open, start and stop the agent, link this computer, change server, quit).
+- The agent: the bundled LLeMbas CLI runs as `lembas service` while the app runs, restarted when
+  it fails and stopped cleanly on quit. A CLI service already running on the computer is used
+  instead of starting a second one.
+- Linking: `lembas login --json` with the approval page shown in the window.
+- Linux packages (`.deb`, AppImage) built by GitHub Actions from a tag.