feat: v0.4.0 - provider icon system, settings modal & polish

- Add provider icon system with extracted icon library (cc-switch based)

- Persist icon and icon_color in SQLite and config.toml

- Add Settings modal (theme / language / update check / silent download)

- Add useTheme and useUpdateCheck hooks

- Add provider icon picker (IconPicker) with search and grid

- Fix icon frame 2-layer color difference in ProviderEdit

- Dashboard heatmap and daily usage improvements

- Sessions page polish and adaptive layout

- Bump version to 0.4.0

src-tauri/src/lib.rs

@@ -100,6 +100,11 @@ pub fn run() {
             commands::get_app_version,
             commands::list_provider_models,
             commands::debug_log,
+            commands::get_app_setting,
+            commands::set_app_setting,
+            commands::check_for_update,
+            commands::download_update,
+            commands::open_installer,
             dashboard::get_paths,
             dashboard::get_prices,
             dashboard::get_summary,