Consolidate all API endpoints under `/api/`

[leandrumartin]

🎯 Goal / Objective

A clear and concise description of what this task aims to achieve. Why is this task important?

Every API endpoint starts with /api/ except for /colored-regions. It would be cleaner for them all to be the same.

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Acceptance Criteria

A checklist of conditions that must be met for this task to be considered complete. How will we verify that it's done correctly?

• The new feature is implemented as described.
• All related code passes the repository's workflow checks (linting, tests).
• The application runs without errors after the changes are made.
• (If applicable) New automated tests have been added to cover the changes.
• Any related documentation has been updated, including JSDoc comments or docstrings