fix(ui): the new-connection wizard uses a hand-built search field #1442

Problem

The Select your database step draws its own search box (magnifier outside the field and a second border), unlike QueryaSearchField in the sidebar and Preferences.

Scope

• Use QueryaSearchField (lg) in new_connection_dialog.dart; keep the live filtering.
• Check the category and database-type dropdowns are QueryaDropdown at lg.

Found while driving a Linux debug build of dev after the button migration (UI consistency review). Part of epic #1331.