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/types/index.ts

@@ -1,3 +1,10 @@
+export type DbFlavor = "postgresql" | "greenplum";
+
+export interface ConnectResult {
+  version: string;
+  flavor: DbFlavor;
+}
+
 export interface ConnectionConfig {
   id: string;
   name: string;