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/infrastructure/src/persistence/cms/conversation_repo.rs

@@ -0,0 +1,34 @@
+//! JSON file–backed `ConversationRepository`.
+//! Stores `Conversation` at `<session_dir>/conversation.json`.
+
+use std::path::Path;
+
+use zesdex_domain::cms::{Conversation, ConversationRepository, RepositoryError};
+
+use crate::utils::write_json_atomic;
+
+/// File-based `ConversationRepository` that reads/writes `conversation.json`.
+#[derive(Debug, Clone, Default)]
+pub struct JsonConversationRepository;
+
+impl JsonConversationRepository {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl ConversationRepository for JsonConversationRepository {
+    fn load(&self, session_dir: &Path) -> Result<Conversation, RepositoryError> {
+        let path = session_dir.join("conversation.json");
+        let data = std::fs::read_to_string(&path)?;
+        let conv: Conversation = serde_json::from_str(&data)?;
+        Ok(conv)
+    }
+
+    fn save(&self, session_dir: &Path, conversation: &Conversation) -> Result<(), RepositoryError> {
+        std::fs::create_dir_all(session_dir)?;
+        let path = session_dir.join("conversation.json");
+        write_json_atomic(&path, conversation, None)?;
+        Ok(())
+    }
+}