feat(frontend): reusable validation schema

[sebastien-comeau]

This commit introduces a robust string validation schema, stringSchema, along with new validation schemas for first name, last name, and email address. These schemas leverage Zod for type safety and offer customizable options including:

• String Length Validation: Enforce minimum and maximum string lengths.
• Format Validation: Predefined formats (alpha-only, alphanumeric, digit-only, non-digit) and custom regular expression support.
• Trimming: Automatic trimming of leading/trailing whitespace (configurable).
• Customizable Error Messages: Tailor error messages for each validation rule.
• 100% Test Coverage: Comprehensive unit tests ensure the reliability and correctness of the validation logic, covering all features and edge cases.

The new schemas (firstNameSchema, lastNameSchema, and emailAddressSchema) build upon the flexible stringSchema to provide specialized validation for common use cases. This improves data integrity and provides a consistent user experience.