Refactor IPC and DTO structures; remove unused code and streamline message handling

- Removed unused structs and methods from `response.rs`, `usage.rs`, and `client.rs`.
- Simplified `Connection` handling in `conn.rs` to only support Unix sockets.
- Updated `IpcServer` to exclusively use Unix sockets and removed TCP handling.
- Cleaned up `editlog.rs` by removing loading and recent entry methods.
- Refactored `memory.rs` to eliminate unused functions related to lesson promotion and retrospective creation.
- Enhanced `search.rs` to support multiple search providers and improved error handling.
- Updated chat view logic to simplify message display and improve user experience.
- Removed deprecated modules and constants from various files to streamline the codebase.

src/model/msglog/mod.rs

@@ -1,4 +1,14 @@
-pub mod blobs;
 pub mod query;
 pub mod schema;
-pub mod summary;
+
+pub use query::insert_message;
+
+pub fn open_or_create(session_dir: &std::path::Path) -> anyhow::Result<rusqlite::Connection> {
+    let path = session_dir.join("messages.sqlite");
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent)?;
+    }
+    let conn = rusqlite::Connection::open(&path)?;
+    schema::init_schema(&conn)?;
+    Ok(conn)
+}