Feat/initial core setup

[Muizzyranking]

Summary

This PR establishes the core architectural foundation for the Flint application. It
implements centralized logging, global exception handling, Redis connectivity, and wires
up the initial API routing structure.

Type of Change

• New Feature
• Chore (folder structure and initial setup)

Key Changes

• Core Wiring: Integrated core modules in app/main.py and implemented lifespan
  for clean startup/shutdown (e.g., closing Redis).
• Exception Handling: Created a robust exception system in
  app/core/exceptions.py and registered global handlers in
  app/core/exception_handlers.py.
• Logging: Configured a centralized logging utility in app/core/logger.py.
• Database: Added Redis connection management in app/db/redis.py.
• Routing: Structured the API with a V1 router in app/api/v1/router.py.
• Schemas: Defined standard API response structures in app/schemas/response.py.

Database Migrations

• This PR includes database migrations (alembic/versions/).
• Migrations have been tested locally.

Testing Strategy

• Manual testing performed (verified / and /health endpoints).
• Base test configuration initialized in tests/conftest.py.

Checklist

• Code follows the project's style guidelines.
• Documentation (in docs/) has been updated where applicable.
• I have verified the changes in a local environment.