Refactor ExecutionService and remove memory tracking

[SeifMohmmed]

Changes:
Simplified the RunCodeAsync method by removing the memoryLimit parameter and all memory tracking logic. Refactored ExecutionService to improve maintainability, including:

• Introduced CleanupAsync for resource cleanup and added IDisposable implementation.
• Updated _containerId to nullable and improved Docker container lifecycle management.
• Consolidated file path handling with consistent naming conventions.
• Simplified Docker command creation to focus on runtime limits.
• Enhanced response classes (AcceptedResponse, WrongAnswerResponse, etc.) with additional fields for better debugging.
• Refactored CalculateResult to use a shared method for reading execution outputs.
• Removed legacy code and unused methods for better maintainability.

Improved error handling, updated Docker container configuration, and enhanced test case handling. These changes make the codebase cleaner, more robust, and easier to extend.