feat: phase 5 distribution — tauri shell, pwa, desktop release artifacts

- apps/desktop: Tauri 2 thin shell; connect screen stores the deployment
  URL, webview renders the remote console, tray with Show/Change Server/
  Quit, close-to-tray, single-instance
- frontend: vite-plugin-pwa generates manifest + Workbox SW (shell
  precache, /api /auth /mailpit NetworkOnly), install banner on
  beforeinstallprompt, rasterized PWA icons
- release.yml: desktop bundle matrix (linux/macos/windows) attached to
  GitHub Releases
- workspace 0.5.0; Dockerfiles copy the desktop workspace manifest

Authored By: TDvorak <[email protected]>

apps/desktop/src-tauri/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "primora-desktop"
+version = "0.5.0"
+edition = "2021"
+description = "Primora desktop shell — thin client for a self-hosted Primora deployment"
+license = "MIT"
+
+[lib]
+name = "primora_desktop_lib"
+crate-type = ["staticlib", "cdylib", "rlib"]
+
+[build-dependencies]
+tauri-build = { version = "2", features = [] }
+
+[dependencies]
+tauri = { version = "2", features = ["tray-icon", "image-png"] }
+tauri-plugin-single-instance = "2"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"