feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/application/src/cms/settings_service.rs

@@ -0,0 +1,76 @@
+//! Settings and app-config use-case implementation.
+//!
+//! `SettingsServiceImpl` implements [`SettingsService`] from the domain
+//! layer. It is generic over `S: SettingsRepository` and `C: AppConfigRepository`,
+//! delegating persistence to those adapters.
+//!
+//! # Flow
+//!
+//! Each method delegates to the appropriate injected repository with the
+//! configured `base_dir`. The `update_provider` method coordinates between
+//! both repositories: load app config → mutate provider map → save app config.
+
+use std::path::PathBuf;
+use tracing;
+
+use zesdex_domain::cms::{
+    AppConfig, AppConfigRepository, ProviderConfig, ServiceError, Settings,
+    SettingsRepository,
+};
+
+/// Service implementation for settings and app-config operations.
+///
+/// Generic over `S: SettingsRepository` and `C: AppConfigRepository` so
+/// the persistence layer can be swapped without changing business logic.
+pub struct SettingsServiceImpl<S, C> {
+    pub settings_repo: S,
+    pub app_config_repo: C,
+    pub base_dir: PathBuf,
+}
+
+impl<S: SettingsRepository, C: AppConfigRepository> SettingsServiceImpl<S, C> {
+    /// Create a new service with the given repositories and base directory.
+    pub fn new(
+        settings_repo: S,
+        app_config_repo: C,
+        base_dir: impl Into<PathBuf>,
+    ) -> Self {
+        tracing::debug!("creating SettingsServiceImpl");
+        Self {
+            settings_repo,
+            app_config_repo,
+            base_dir: base_dir.into(),
+        }
+    }
+}
+
+impl<S: SettingsRepository, C: AppConfigRepository>
+    zesdex_domain::cms::SettingsService for SettingsServiceImpl<S, C>
+{
+    fn load_settings(&self) -> Result<Settings, ServiceError> {
+        tracing::debug!("loading settings");
+        self.settings_repo
+            .load(&self.base_dir)
+            .map_err(ServiceError::Repository)
+    }
+
+    fn save_settings(&self, settings: &Settings) -> Result<(), ServiceError> {
+        tracing::debug!("saving settings");
+        self.settings_repo.save(&self.base_dir, settings)?;
+        Ok(())
+    }
+
+    fn update_provider(
+        &self,
+        name: &str,
+        config: &ProviderConfig,
+    ) -> Result<(), ServiceError> {
+        tracing::debug!("updating provider '{name}'");
+        let mut app_config: AppConfig = self.app_config_repo.load(&self.base_dir)?;
+        app_config
+            .providers
+            .insert(name.to_string(), config.clone());
+        self.app_config_repo.save(&self.base_dir, &app_config)?;
+        Ok(())
+    }
+}