Support fleet filters in the Offers and Launch UI

[peterschmidt85]

Summary

Offers

• Add fleet filtering to the Offers page.
• Keep the current unscoped behavior when no fleet is selected.
• Scope grouped offers to selected fleets when one or more fleets are set.
• Support imported fleets using the same project/name format as the CLI.
• Preserve selected fleets in the URL.

Launch

• Add the same fleet filter to the Launch resource picker.
• Write selected fleets to generated YAML as configuration.fleets, following the existing backend flow.

Property filter

• Load dynamic property-filter values when the filter menu opens instead of only after typing.
• Apply this to project, user, and fleet values.
• Keep the existing 100-item cap while narrowing results as the user types.

AI Assistance

• Assisted by Codex