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/models/management.rs

@@ -79,6 +79,19 @@ pub struct TablePrivilege {
     pub is_grantable: bool,
 }
 
+#[derive(Debug, Serialize, Deserialize)]
+pub struct SessionInfo {
+    pub pid: i32,
+    pub usename: Option<String>,
+    pub datname: Option<String>,
+    pub state: Option<String>,
+    pub query: Option<String>,
+    pub query_start: Option<String>,
+    pub wait_event_type: Option<String>,
+    pub wait_event: Option<String>,
+    pub client_addr: Option<String>,
+}
+
 #[derive(Debug, Deserialize)]
 pub struct GrantRevokeParams {
     pub action: String,

src-tauri/src/models/mod.rs

@@ -2,4 +2,5 @@ pub mod connection;
 pub mod history;
 pub mod management;
 pub mod query_result;
+pub mod saved_queries;
 pub mod schema;

src-tauri/src/models/saved_queries.rs

@@ -0,0 +1,10 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SavedQuery {
+    pub id: String,
+    pub name: String,
+    pub sql: String,
+    pub connection_id: Option<String>,
+    pub created_at: String,
+}

src-tauri/src/models/schema.rs

@@ -5,6 +5,8 @@ pub struct SchemaObject {
     pub name: String,
     pub object_type: String,
     pub schema: String,
+    pub row_count: Option<i64>,
+    pub size_bytes: Option<i64>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -18,6 +20,15 @@ pub struct ColumnInfo {
     pub is_primary_key: bool,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ColumnDetail {
+    pub column_name: String,
+    pub data_type: String,
+    pub is_nullable: bool,
+    pub column_default: Option<String>,
+    pub is_identity: bool,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ConstraintInfo {
     pub name: String,