Fix desktop crate build; simplify tray/menu and telemetry reconnect

Real bugs found by actually compiling the Tauri crate for the first time:
- Cargo.toml declared a [lib] with no src/lib.rs (cargo refused to parse
  the manifest) — added the standard Tauri 2 main.rs/lib.rs split.
- generate_context!() needs real icon files; icons/ only had a .gitkeep.
  Added placeholder PNG/ICO/ICNS icons.

Also simplified: dropped the tray icon + menu (one more moving part not
needed yet), and the telemetry store's exponential backoff is now a fixed
3s retry, matching the same simplification made to continuum-proxy's
uplink client.

Fixed two real TS bugs while typechecking apps/web for the first time
(missing @types/node for nuxt.config.ts's process.env access, untyped
useFetch call inferring 'never'). Verified: cargo check (desktop),
vue-tsc --noEmit (web + ui packages) all clean.

apps/desktop/src-tauri/Cargo.toml

@@ -9,7 +9,7 @@ rust-version = "1.77"
 tauri-build = { version = "2.0", features = [] }
 
 [dependencies]
-tauri = { version = "2.1", features = ["tray-icon"] }
+tauri = "2.1"
 tauri-plugin-fs = "2.0"
 tauri-plugin-shell = "2.0"
 serde = { version = "1", features = ["derive"] }

apps/desktop/src-tauri/src/lib.rs

@@ -0,0 +1,12 @@
+// This is intentionally the plainest possible Tauri shell: load the two
+// plugins the desktop app needs (filesystem access, opening external links)
+// and show the window. A tray icon with a menu is a natural next addition
+// once this makes sense — see Tauri's tray-icon docs when you're ready.
+#[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub fn run() {
+    tauri::Builder::default()
+        .plugin(tauri_plugin_fs::init())
+        .plugin(tauri_plugin_shell::init())
+        .run(tauri::generate_context!())
+        .expect("error while running the Continuum desktop shell");
+}

apps/desktop/src-tauri/src/main.rs

@@ -1,39 +1,6 @@
 // Prevents an additional console window on Windows in release builds.
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
-use tauri::{
-    menu::{Menu, MenuItem},
-    tray::TrayIconBuilder,
-    Manager,
-};
-
 fn main() {
-    tauri::Builder::default()
-        .plugin(tauri_plugin_fs::init())
-        .plugin(tauri_plugin_shell::init())
-        .setup(|app| {
-            let show = MenuItem::with_id(app, "show", "Show Continuum", true, None::<&str>)?;
-            let quit = MenuItem::with_id(app, "quit", "Quit", true, None::<&str>)?;
-            let menu = Menu::with_items(app, &[&show, &quit])?;
-
-            TrayIconBuilder::new()
-                .icon(app.default_window_icon().unwrap().clone())
-                .menu(&menu)
-                .tooltip("Continuum — print farm console")
-                .on_menu_event(|app, event| match event.id.as_ref() {
-                    "show" => {
-                        if let Some(window) = app.get_webview_window("main") {
-                            let _ = window.show();
-                            let _ = window.set_focus();
-                        }
-                    }
-                    "quit" => app.exit(0),
-                    _ => {}
-                })
-                .build(app)?;
-
-            Ok(())
-        })
-        .run(tauri::generate_context!())
-        .expect("error while running the Continuum desktop shell");
+    continuum_desktop_lib::run();
 }

apps/desktop/src-tauri/tauri.conf.json

@@ -23,10 +23,6 @@
     ],
     "security": {
       "csp": null
-    },
-    "trayIcon": {
-      "iconPath": "icons/icon.png",
-      "iconAsTemplate": true
     }
   },
   "bundle": {