[Enhancement]: Harden Upload form client-side validation

[tomvothecoder]

Is your feature request related to a problem?

This is a pre-release hardening effort for the Upload form. Some validation already exists, but it should be more carefully reviewed, tested, and made consistent. Backend validation logic should remain unchanged; frontend validation should mirror existing backend constraints where possible.

Describe the solution you'd like

Strengthen and more carefully audit the existing client-side validation in the Upload form, building on the current implementation.

Specifically:

• Review and tighten required field checks to ensure they are consistently enforced
  • Metadata field not working correctly (refer to comment)
• Improve validation of input formats where applicable (URLs vs URIs, JSON validity, date fields and ordering)
• Ensure validation logic is aligned with backend constraints (refer to FastAPI models)
• Display clear, inline, field-level validation messages
  • Duplicate simulations -- check simulation name in the database when user types it in
  • Incorrect entries for GitHub URL
  • Incorrect entries for output path URL (must be public URL or HPC filepath)
• Provide a top-level validation summary when multiple issues are present
  • Display errors in the review and submit
• Prevent submission when validation fails (e.g., disable submit button)

Describe alternatives you've considered

Additional context