[TASK 3.1.2] Validate portfolio creation inputs.

[catapam]

Ensure that the portfolio name and initial capital fields are valid before allowing the user to create the portfolio.

Acceptance Criteria:

• [x] The portfolio name is validated for uniqueness and length.
• [x] The initial capital is validated as a positive number.

Steps:

1. Implement validation logic for the portfolio name (e.g., uniqueness, length).
2. Implement validation logic for the initial capital (e.g., positive number).
3. Display appropriate error messages for invalid inputs.

Linked Issues:

• 7

• 8

• Documentation: Portfolio Creation Validation Documentation

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[catapam]

commit The capital letter was changed for color, uniqueness has been considered unnecessary for this