[Chore]: Remove unused placeholder files and legacy model code

[Sandesh282]

Description:

Several files in the codebase are either empty placeholders, unused stubs, or legacy implementations that have been fully superseded by newer code. These files add confusion for contributors and should be removed.

Files to Remove:

File	Reason for Removal
CForge/Views/ContestComponent.swift	Placeholder stub containing only "Hello, World!" -- not referenced anywhere
CForge/Models/CFContests.swift	Legacy model with hardcoded sample data -- replaced by Views/Contest/ContestModels.swift
CForge/Models/CFProblem.swift	Legacy model with hardcoded sample data -- replaced by Views/Problem/ProblemModels.swift
CForge/Models/CFUser.swift	Legacy model with hardcoded sample data -- replaced by Views/Profile/ProfileModels.swift
CForge/Models/API/Utilities/NetworkManager.swift	Old callback-based singleton -- replaced by async/await ProblemService and direct URLSession usage
CForge/Utilities/Extension/String+Extensions.swift	Completely empty file with no content

Steps to Fix:

1. Delete each file listed above from the project.
2. If Xcode shows red (missing) references in the project navigator, right-click and select Delete to remove them from the .xcodeproj.
3. Build the project (Cmd+B) to confirm nothing is broken.
4. Run the app on a simulator to verify all features still work correctly.

Expected Outcome:

• All 6 unused files are removed from the repository.
• The project compiles and runs without errors.
• No functionality is affected since none of these files are referenced by active code.