Create database schema and migration scripts

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Goal

Set up the initial relational schema (or document store collections) for the REST API and generate migration files that can be run locally and in CI/CD.

Tasks

• Define tables/collections for Users, Roles, Tokens, and any domain entities needed by the first version of the API.
• Utilize Phinx for migrations and add it as a Composer dependency.
• Write migration scripts for:
  • users table
  • roles table (if applicable)
  • jwt_blacklist or refresh_tokens table (optional, for revocation)
• Ensure migrations are idempotent and can be rolled back.
• Add a migrate shortcut script to composer.json for developers.

Acceptance Criteria

• Running composer migrate creates the full schema on a fresh DB.
• All migrations have clear documentation/comments.
• CI pipeline runs migrations against a test database without errors.

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Implemented #10