feat: add column sort, SQL formatter, table stats, insert dialog, saved queries & sessions monitor

- Column sort by header click in table view (ASC/DESC/none cycle, server-side)
- SQL formatter with Format button and Shift+Alt+F keybinding (sql-formatter)
- Table size and row count display in schema tree via pg_class
- Insert row dialog with column type hints and auto-skip for identity columns
- Saved queries (bookmarks) with CRUD backend, sidebar panel, and save dialog
- Active sessions monitor (pg_stat_activity) with auto-refresh, cancel & terminate

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/commands/management.rs

@@ -507,3 +507,83 @@ pub async fn manage_role_membership(
 
     Ok(())
 }
+
+#[tauri::command]
+pub async fn list_sessions(
+    state: State<'_, AppState>,
+    connection_id: String,
+) -> TuskResult<Vec<SessionInfo>> {
+    let pools = state.pools.read().await;
+    let pool = pools
+        .get(&connection_id)
+        .ok_or(TuskError::NotConnected(connection_id))?;
+
+    let rows = sqlx::query(
+        "SELECT pid, usename, datname, state, query, \
+                query_start::text, wait_event_type, wait_event, \
+                client_addr::text \
+         FROM pg_stat_activity \
+         WHERE datname IS NOT NULL \
+         ORDER BY query_start DESC NULLS LAST",
+    )
+    .fetch_all(pool)
+    .await
+    .map_err(TuskError::Database)?;
+
+    let sessions = rows
+        .iter()
+        .map(|row| SessionInfo {
+            pid: row.get("pid"),
+            usename: row.get("usename"),
+            datname: row.get("datname"),
+            state: row.get("state"),
+            query: row.get("query"),
+            query_start: row.get("query_start"),
+            wait_event_type: row.get("wait_event_type"),
+            wait_event: row.get("wait_event"),
+            client_addr: row.get("client_addr"),
+        })
+        .collect();
+
+    Ok(sessions)
+}
+
+#[tauri::command]
+pub async fn cancel_query(
+    state: State<'_, AppState>,
+    connection_id: String,
+    pid: i32,
+) -> TuskResult<bool> {
+    let pools = state.pools.read().await;
+    let pool = pools
+        .get(&connection_id)
+        .ok_or(TuskError::NotConnected(connection_id))?;
+
+    let row = sqlx::query("SELECT pg_cancel_backend($1)")
+        .bind(pid)
+        .fetch_one(pool)
+        .await
+        .map_err(TuskError::Database)?;
+
+    Ok(row.get::<bool, _>(0))
+}
+
+#[tauri::command]
+pub async fn terminate_backend(
+    state: State<'_, AppState>,
+    connection_id: String,
+    pid: i32,
+) -> TuskResult<bool> {
+    let pools = state.pools.read().await;
+    let pool = pools
+        .get(&connection_id)
+        .ok_or(TuskError::NotConnected(connection_id))?;
+
+    let row = sqlx::query("SELECT pg_terminate_backend($1)")
+        .bind(pid)
+        .fetch_one(pool)
+        .await
+        .map_err(TuskError::Database)?;
+
+    Ok(row.get::<bool, _>(0))
+}