[FEAT_REQ] Refactor repromodel_core > app.py

[tomonarifeehan]

Is your feature request related to a problem? Please describe.
The app.py file currently contains a large amount of code that mixes various functionalities, making it difficult to maintain, test, and extend. The file includes numerous imports, constants, initialization code, and endpoint definitions, leading to a lack of clear separation of concerns. This increases the complexity of debugging and adds challenges when implementing new features or refactoring existing ones.

Describe the solution you'd like
Refactor the app.py file by organizing it into smaller, modular components. Key improvements should include:

• Separation of Concerns: Split the code into separate modules for initialization, route definitions, utility functions, and constants. This will improve maintainability and readability.
• Code Cleanup: Remove redundant imports and unused code segments. Consolidate duplicate logic, such as repeated error handling and process checking.
• Improved Structure: Create a well-defined folder structure for routing, middleware, services, and utilities. This will make the codebase easier to navigate and enhance code reuse.
• Add Comments and Documentation: Provide clear comments and documentation throughout the code to explain the purpose of each module and function.
• Describe alternatives you’ve considered
• Keeping the existing structure but adding more comments and minor reorganizations; however, this would only provide a temporary improvement and not address the underlying maintainability issues.
• Breaking the code into classes, though it might complicate the structure unnecessarily given the current setup.

Additional context
Refactoring the app.py file will lead to a cleaner, more maintainable codebase that is easier to test and extend. The modular design will facilitate future updates and integrations, improving overall development velocity. Below are examples of best practices for organizing large Flask applications that could be used as a reference during the refactoring process.