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/conversation_service.rs

@@ -0,0 +1,72 @@
+//! Conversation use-case implementation.
+//!
+//! `ConversationServiceImpl` implements [`ConversationService`] from the
+//! domain layer. It is generic over `R: ConversationRepository`, delegating
+//! all persistence to that adapter.
+//!
+//! # Flow
+//!
+//! Each method computes the session directory from the session ID, then
+//! delegates the actual I/O to the injected `repo`. Error context is
+//! added at this layer to identify which session caused the failure.
+
+use std::path::PathBuf;
+use tracing;
+
+use zesdex_domain::cms::{Conversation, ConversationRepository, ServiceError};
+use zesdex_domain::core::ChatMessage;
+
+/// Service implementation for conversation CRUD operations.
+///
+/// Generic over `R: ConversationRepository` so the persistence layer
+/// can be swapped without changing business logic.
+pub struct ConversationServiceImpl<R> {
+    pub repo: R,
+    /// Base directory containing session subdirectories.
+    pub sessions_dir: PathBuf,
+}
+
+impl<R: ConversationRepository> ConversationServiceImpl<R> {
+    /// Create a new service with the given repository and sessions directory.
+    pub fn new(repo: R, sessions_dir: impl Into<PathBuf>) -> Self {
+        tracing::debug!("creating ConversationServiceImpl");
+        Self {
+            repo,
+            sessions_dir: sessions_dir.into(),
+        }
+    }
+
+    /// Compute the session directory for a given session id.
+    fn session_dir(&self, session_id: &str) -> PathBuf {
+        self.sessions_dir.join(session_id)
+    }
+}
+
+impl<R: ConversationRepository> zesdex_domain::cms::ConversationService
+    for ConversationServiceImpl<R>
+{
+    fn load_conversation(&self, session_id: &str) -> Result<Conversation, ServiceError> {
+        tracing::debug!("loading conversation for session {session_id}");
+        let dir = self.session_dir(session_id);
+        self.repo.load(&dir).map_err(ServiceError::Repository)
+    }
+
+    fn save_conversation(&self, conv: &Conversation) -> Result<(), ServiceError> {
+        tracing::debug!("saving conversation for session {}", conv.session_id);
+        let dir = self.session_dir(&conv.session_id);
+        self.repo.save(&dir, conv)?;
+        Ok(())
+    }
+
+    fn add_message(
+        &self,
+        conv: &mut Conversation,
+        msg: ChatMessage,
+    ) -> Result<(), ServiceError> {
+        tracing::debug!("adding message to session {}", conv.session_id);
+        conv.push(msg);
+        let dir = self.session_dir(&conv.session_id);
+        self.repo.save(&dir, conv)?;
+        Ok(())
+    }
+}