feat(tauri-app): expand tray menu + open_external_url + Profile/Search items

Tray menu now has:
  Show maarcadetweet
  Home
  Compose
  Profile
  Search
  ----
  Quit

The Home/Profile/Search items emit 'app://navigate' events
which the frontend's listenTrayEvents translates to view
switches. The compose and show events continue to be
separate event types ('app://compose', 'app://show').

open_external_url Tauri command takes a URL, validates it's
http(s), and uses tauri-plugin-shell to open it in the user's
default browser. The frontend's openExternalUrl falls back
to window.open in the browser preview (no Tauri runtime).

svelte-check error fix: tauriCall<T>(cmd, fallback, args?)
had the second call argument as 'undefined' instead of 'null'
on the call site for session.load(). The TypeScript compiler
correctly noted that the fallback type 'T' (here Session |
null) couldn't be undefined. Replaced with 'null' and
dropped the trailing null args argument (it's optional).

crates/tauri-app/src-tauri/src/lib.rs

@@ -444,6 +444,28 @@ async fn pick_and_upload_image(
     Ok(Some(resp))
 }
 
+/// Open an external URL in the user's default browser. Returns
+/// silently on success. Only accepts `http://` and `https://` —
+/// any other scheme (e.g. `file://`, `mailto:`, `javascript:`)
+/// is rejected so the Rust side is the single source of truth for
+/// which schemes are allowed.
+#[tauri::command]
+async fn open_external_url(
+    url: String,
+    app: tauri::AppHandle,
+) -> Result<(), String> {
+    use tauri_plugin_shell::ShellExt;
+    let lower = url.to_ascii_lowercase();
+    if !(lower.starts_with("http://") || lower.starts_with("https://")) {
+        return Err(format!(
+            "open_external_url: refusing non-http(s) scheme in {url:?}"
+        ));
+    }
+    app.shell()
+        .open(url, None)
+        .map_err(|e| e.to_string())
+}
+
 /// Map a file extension to a MIME type. Returns
 /// `application/octet-stream` when the extension is unrecognised —
 /// the PDS's magic-byte sniffer will take over from there.
@@ -529,6 +551,7 @@ pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_notification::init())
         .plugin(tauri_plugin_dialog::init())
+        .plugin(tauri_plugin_shell::init())
         .plugin(tauri_plugin_updater::Builder::new().build())
         .plugin(tauri_plugin_window_state::Builder::default().build())
         .manage(state)
@@ -551,6 +574,14 @@ pub fn run() {
                 None::<&str>,
             )
             .map_err(|e| format!("failed to build show menu item: {e}"))?;
+            let home_item = tauri::menu::MenuItem::with_id(
+                app,
+                "tray_home",
+                "Home",
+                true,
+                None::<&str>,
+            )
+            .map_err(|e| format!("failed to build home menu item: {e}"))?;
             let compose_item = tauri::menu::MenuItem::with_id(
                 app,
                 "tray_compose",
@@ -559,6 +590,22 @@ pub fn run() {
                 None::<&str>,
             )
             .map_err(|e| format!("failed to build compose menu item: {e}"))?;
+            let profile_item = tauri::menu::MenuItem::with_id(
+                app,
+                "tray_profile",
+                "Profile",
+                true,
+                None::<&str>,
+            )
+            .map_err(|e| format!("failed to build profile menu item: {e}"))?;
+            let search_item = tauri::menu::MenuItem::with_id(
+                app,
+                "tray_search",
+                "Search",
+                true,
+                None::<&str>,
+            )
+            .map_err(|e| format!("failed to build search menu item: {e}"))?;
             let quit_item = tauri::menu::MenuItem::with_id(
                 app,
                 "tray_quit",
@@ -572,7 +619,15 @@ pub fn run() {
 
             let tray_menu = tauri::menu::Menu::with_items(
                 app,
-                &[&show_item, &compose_item, &separator, &quit_item],
+                &[
+                    &show_item,
+                    &home_item,
+                    &compose_item,
+                    &profile_item,
+                    &search_item,
+                    &separator,
+                    &quit_item,
+                ],
             )
             .map_err(|e| format!("failed to build tray menu: {e}"))?;
 
@@ -586,9 +641,18 @@ pub fn run() {
                     "tray_show" => {
                         let _ = tauri::Emitter::emit(app, "app://show", ());
                     }
+                    "tray_home" => {
+                        let _ = tauri::Emitter::emit(app, "app://navigate", "home");
+                    }
                     "tray_compose" => {
                         let _ = tauri::Emitter::emit(app, "app://compose", ());
                     }
+                    "tray_profile" => {
+                        let _ = tauri::Emitter::emit(app, "app://navigate", "profile");
+                    }
+                    "tray_search" => {
+                        let _ = tauri::Emitter::emit(app, "app://navigate", "search");
+                    }
                     "tray_quit" => {
                         app.exit(0);
                     }
@@ -634,6 +698,7 @@ pub fn run() {
             fetch_blob,
             pick_and_upload_image,
             show_notification,
+            open_external_url,
         ])
         .run(tauri::generate_context!())
         .expect("error while running maarcadetweet");