refactor(ui): migrate dialogs and forms to QueryaButton and QueryaDialogActions #1338

Part of #1331. Needs QueryaDialogActions.

Scope

• Every dialog footer (connection forms x5, update, welcome tour, preferences, theme editor, SQL editor dialogs, query history, unsaved-work guard, ERD dialogs, Mongo / Redis dialogs, QueryaModalDialog, QueryaConfirmDialog) uses QueryaDialogActions: Cancel is always ghost, the main action primary, irreversible destructive, all lg.
• Inconsistencies from the review made uniform: Close (primary 5x, outline 6x, ghost 3x), Retry (outline 15x, primary 1x), Create (small 3x, normal 3x), Cancel (ghost 21x, outline 11x).
• Test Connection and other inline form actions: secondary lg, with the loading state of the button, not a separate spinner.
• Esc / Enter behave the same in every dialog (through the footer).

Acceptance

• A scan of lib/ finds no shadcn button in a dialog.
• Each dialog has exactly one primary or destructive button (test over the dialog list in the gallery).
• Existing form and e2e tests pass unchanged apart from finders by type.