feat(grokbuild): add first-class Grok Build support (#5453)

* feat(grokbuild): add backend integration

* feat(grokbuild): add provider and management UI

* test(grokbuild): cover configuration and integrations

* fix(grokbuild): address backend review feedback

* fix(grokbuild): complete UI review feedback

* feat(grokbuild): add CLI lifecycle management

* fix(grokbuild): align provider icon fallback

* test(grokbuild): cover provider icon persistence

src-tauri/src/database/tests.rs

@@ -517,7 +517,7 @@ fn schema_create_tables_repairs_legacy_proxy_config_singleton_to_per_app() {
     let count: i32 = conn
         .query_row("SELECT COUNT(*) FROM proxy_config", [], |r| r.get(0))
         .expect("count rows");
-    assert_eq!(count, 3, "per-app proxy_config should have 3 rows");
+    assert_eq!(count, 4, "per-app proxy_config should have 4 rows");
 
     // 新结构下应能按 app_type 查询
     let _: i32 = conn
@@ -657,7 +657,7 @@ fn migration_from_v3_8_schema_v1_to_current_schema_v3() {
     let proxy_rows: i64 = conn
         .query_row("SELECT COUNT(*) FROM proxy_config", [], |r| r.get(0))
         .expect("count proxy_config rows");
-    assert_eq!(proxy_rows, 3);
+    assert_eq!(proxy_rows, 4);
 
     // model_pricing 应具备默认数据（迁移时会 seed）
     let pricing_rows: i64 = conn