feat: registration endpoint with Python 3.14 upgrade and refactor

[mobal]

🚀 Features

• Docker support: Added production-ready Dockerfile (c0b349e)
• Registration endpoint: Implemented /register API endpoint (5e3ef14)
• Error handling: Unified error response format with timestamp and error field (187b544)
• Configuration: Added .env.example and multi-file env support (a288b04, 7fbb0f3)
• Token response: Added standardized TokenResponse schema (11b0af2)
• CI/CD: Refreshed GitHub Actions workflow with tflint and ty (bb903f3, 9bdc0fe)

🔧 Refactor

• Code organization:
  • Routers moved to api/v1 package (72d5b12)
  • Services, repositories, models separated into packages (a97b2d9)
  • Terraform files moved to infrastructure/ directory (8ba3456)
• Environment: Preserve previously loaded env vars (479f9ca)
• Testing: Removed deprecated pytest_configure (9ba08c1)
• Code quality: Formatting with ruff (9cda736)

⚡ Performance & Maintenance

• Python upgrade: 3.13 → 3.14 with dependency updates (e72e63c)
• Dependencies: Updated packages and added boto3-stubs (57c8759, 0793c2d, eacc799, 5b77285, e75d915)
• Gitignore: Updated with new patterns (3843875)
• CI: Removed ty as default job (d691c91)
• SonarQube: Disabled verbose logging (9203d66)

🐛 Bug Fixes

• Registration: Fixed password handling during registration (39ab82b)
• Python version: Corrected version number in config (1737593)
• Display name: Set to optional field (c8e2f14)

✅ Tests

• Fixed and updated integration tests (489addf)