fix(ui): persist trigger type selection in GitHub provider forms

[AminDhouib]

1:1 port of upstream Dokploy#4937 by @narcisonunez.

The Trigger Type Select in the GitHub provider forms (application and compose) passed both defaultValue and a controlled value, and forwarded field.onChange directly. Radix emits an empty-string change when the select closes/resets, which wiped the selection. The handler now ignores empty values, and the redundant defaultValue is dropped so the field stays controlled.

Applied verbatim to both save-github-provider.tsx and save-github-provider-compose.tsx; no fork adaptations were needed.