Modernize FirstTimeProxmoxSetup.sh to use shared utilities

[coelacant1]

Description

Host/Bulk/FirstTimeProxmoxSetup.sh is a complex initial setup wizard that has not been updated to use the current shared utility framework. As a critical onboarding script, it should follow the same patterns as other modernized scripts for consistency and maintainability.

Acceptance Criteria

• Script uses ArgumentParser.sh for argument handling where applicable
• Sources shared utilities consistently
• Interactive wizard flow preserved
• Setup steps documented in script header
• Compatible with remote execution via the GUI/CLI menu systems