bug: implement comprehensive form validation for circle creation

[devmocrea]

Description

Add thorough validation to frontend inputs during circle creation to prevent invalid contract call reverts.

Technical Specification

• Validate that the Circle Name is between 3 and 50 characters.
• Ensure the Celo/STX contribution amounts are positive decimals.
• Validate that all member entries match valid Celo hex addresses or Stacks SP... addresses before enabling the submit button.

Acceptance Criteria

• Clear validation error messages show below fields if inputs are invalid.
• Invalid transaction calls are blocked at the frontend level.