feat(06-01): scaffold apps/desktop as @tessera/desktop Tauri 2.x project

- Create Tauri project structure with Cargo.toml, tauri.conf.json, build.rs
- Implement lib.rs with store plugin and server URL navigation on startup
- Configure capabilities with core:default and store:default permissions
- Set frontendDist to ../src for local setup page (no bundled frontend)
- Add placeholder icons for build compatibility (to be replaced in 06-02)
- Add Cargo target/ to .gitignore
- Window config: 1280x800, centered, native decorations, resizable

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -0,0 +1,36 @@
+use tauri::Manager;
+use tauri_plugin_store::StoreExt;
+
+/// Main entry point for the Tessera desktop application.
+///
+/// Registers plugins, checks for a stored server URL on startup,
+/// and either navigates to the configured server or shows the
+/// bundled setup page for first-run configuration.
+pub fn run() {
+    tauri::Builder::default()
+        .plugin(tauri_plugin_store::Builder::new().build())
+        .setup(|app| {
+            // Attempt to read a previously stored server URL
+            let store = app.store("config.json")?;
+            let server_url = store.get("server_url");
+
+            if let Some(url_value) = server_url {
+                if let Some(url_str) = url_value.as_str() {
+                    if !url_str.is_empty() {
+                        // Navigate the main window to the configured server URL
+                        if let Some(window) = app.get_webview_window("main") {
+                            if let Ok(parsed) = url_str.parse::<tauri::Url>() {
+                                let _ = window.navigate(parsed);
+                            }
+                        }
+                    }
+                }
+            }
+            // If no server_url is stored, the WebView remains on the
+            // bundled setup page (frontendDist = ../src/setup.html)
+
+            Ok(())
+        })
+        .run(tauri::generate_context!())
+        .expect("error while running Tessera desktop application");
+}