Refactor/backend/cleanup and deps update

[yumeangelica]

• Updated application dependencies for improved performance and security.
• Removed development routes in app.js to enhance application security.
• Removed getAllPets and getPetById functions from petController and corresponding route to clean codebase.
• Removed getAllUsers function from userController and added comments for future consideration on getUserByName function.
• Refactored tzIdentifierChecker helper to utilize the latest moment-timezone library json for accurate timezone validation.
• Cleaned up petModel by removing unused methods, simplifying model structure for better maintainability.