Implement reviews and rating workflow

[FriggemannMichael]

Objective:
Implement review listing, creation, update, and deletion.

Acceptance criteria:

• GET /api/reviews/ supports business_user_id, reviewer_id, and ordering filters.
• POST /api/reviews/ requires a customer user.
• A customer can review the same business user only once.
• PATCH /api/reviews/{id}/ only allows rating and description updates by the review owner.
• DELETE /api/reviews/{id}/ is restricted to the review owner.
• Responses include id, business_user, reviewer, rating, description, created_at, and updated_at.

[FriggemannMichael]

TDD workflow for this project:

• Define the expected behavior before implementing the endpoint or model behavior.
• Write or outline the failing test first.
• Implement only enough code to make that test pass.
• Refactor after the test passes.
• Keep Django check, Ruff, and the relevant tests green from the local virtual environment.