Generate project IDs during resume import

[DaKheera47]

Summary

• Generate IDs for imported project items before saving Resume Studio documents
• Apply the fix to both Reactive Resume imports and file/AI imports used by onboarding and Resume Studio
• Preserve existing non-empty project IDs and keep the change scoped to import-time repair

Testing

• Added unit coverage for Reactive Resume import and file import paths
• Added regression coverage for blank, whitespace-only, missing, and preserved project IDs
• Full orchestrator test suite passed