This commit addresses several high-priority tasks from the TASKS.md file, including:
- **Fix Background Job Panic:** Replaced `log.Fatalf` with `log.Printf` in the `asynq` server to prevent crashes.
- **Refactor API Server Setup:** Consolidated the GraphQL Playground and Prometheus metrics endpoints into the main API server.
- **Implement `DeleteUser` Mutation:** Implemented the `DeleteUser` resolver.
- **Implement `CreateContribution` Mutation:** Implemented the `CreateContribution` resolver and its required application service.
Additionally, this commit includes a major refactoring of the configuration management system to fix a broken build. The global `config.Cfg` variable has been removed and replaced with a dependency injection approach, where the configuration object is passed to all components that require it. This change has been applied across the entire codebase, including the test suite, to ensure a stable and testable application.
