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/types/index.ts

@@ -29,6 +29,16 @@ export interface SchemaObject {
   name: string;
   object_type: string;
   schema: string;
+  row_count?: number;
+  size_bytes?: number;
+}
+
+export interface ColumnDetail {
+  column_name: string;
+  data_type: string;
+  is_nullable: boolean;
+  column_default: string | null;
+  is_identity: boolean;
 }
 
 export interface ColumnInfo {
@@ -186,7 +196,27 @@ export interface RoleMembershipParams {
   member_name: string;
 }
 
-export type TabType = "query" | "table" | "structure" | "roles";
+export interface SessionInfo {
+  pid: number;
+  usename: string | null;
+  datname: string | null;
+  state: string | null;
+  query: string | null;
+  query_start: string | null;
+  wait_event_type: string | null;
+  wait_event: string | null;
+  client_addr: string | null;
+}
+
+export interface SavedQuery {
+  id: string;
+  name: string;
+  sql: string;
+  connection_id?: string;
+  created_at: string;
+}
+
+export type TabType = "query" | "table" | "structure" | "roles" | "sessions";
 
 export interface Tab {
   id: string;