feat: add Greenplum 7 compatibility and AI SQL generation

Greenplum 7 (PG12-based) compatibility:
- Auto-detect GP via version() string, store DbFlavor per connection
- connect returns ConnectResult with version + flavor
- Fix pg_total_relation_size to use c.oid (universal, safer on both PG/GP)
- Branch is_identity column query for GP (lacks the column)
- Branch list_sessions wait_event fields for GP
- Exclude gp_toolkit schema in schema listing, completion, lookup, AI context
- Smart StatusBar version display: GP shows "GP 7.0.0 (PG 12.4)"
- Fix connection list spinner showing on all cards during connect

AI SQL generation (Ollama):
- Add AI settings, model selection, and generate_sql command
- Frontend AI panel with prompt input and SQL output

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

src-tauri/src/commands/management.rs

@@ -1,6 +1,6 @@
 use crate::error::{TuskError, TuskResult};
 use crate::models::management::*;
-use crate::state::AppState;
+use crate::state::{AppState, DbFlavor};
 use crate::utils::escape_ident;
 use sqlx::Row;
 use std::sync::Arc;
@@ -514,22 +514,32 @@ pub async fn list_sessions(
     state: State<'_, Arc<AppState>>,
     connection_id: String,
 ) -> TuskResult<Vec<SessionInfo>> {
+    let flavor = state.get_flavor(&connection_id).await;
     let pools = state.pools.read().await;
     let pool = pools
         .get(&connection_id)
         .ok_or(TuskError::NotConnected(connection_id))?;
 
-    let rows = sqlx::query(
+    let sql = if flavor == DbFlavor::Greenplum {
+        "SELECT pid, usename, datname, state, query, \
+                query_start::text, NULL::text as wait_event_type, NULL::text as wait_event, \
+                client_addr::text \
+         FROM pg_stat_activity \
+         WHERE datname IS NOT NULL \
+         ORDER BY query_start DESC NULLS LAST"
+    } else {
         "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)?;
+         ORDER BY query_start DESC NULLS LAST"
+    };
+
+    let rows = sqlx::query(sql)
+        .fetch_all(pool)
+        .await
+        .map_err(TuskError::Database)?;
 
     let sessions = rows
         .iter()