fix: Improve error message for URL conflicts

[rafaelrsantosti]

Description

Improve the user experience when a URL conflict occurs during application component creation.

Current Behavior

When a user tries to create a component with a URL that already exists, they receive a generic database constraint error that is not user-friendly.

Expected Behavior

Show a clear, actionable error message like:

"The URL 'myapp.localhost' is already in use by another application. Please choose a different URL."

Implementation

1. API: Catch the unique constraint violation and return a specific error code
2. Portal: Display a friendly error message with suggestion to change the URL

Acceptance Criteria

• API returns HTTP 409 (Conflict) with clear message
• Portal shows user-friendly error
• Error suggests available alternatives (optional)

Related Issues

• feat: Automatic URL generation for applications #45 (Automatic URL generation will reduce these conflicts)

[Abdulrahman295]

Hi @rafaelrsantosti 👋

I'd like to work on this issue.