Add difficulty levels to Hangman and Number Guessing

[avzuha]

📝 Description

This PR adds selectable difficulty levels to both the Number Guessing and Hangman games, improving replayability and providing a progressive challenge for users.

Number Guessing

• Added a difficulty selection screen before starting the game.
• Easy: Number range 1–100 with 10 attempts.
• Medium: Number range 1–100 with 7 attempts.
• Hard: Number range 1–200 with 5 attempts.
• Added attempt-limit game over logic.

Hangman

• Added a difficulty selection screen before starting the game.
• Easy: Short, common words.
• Medium: Existing word list.
• Hard: Longer technical/programming-related words.

These changes allow users to choose a challenge level that matches their experience while preserving the original gameplay through the Medium difficulty option

Closes #641

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📋 Contribution Checklist

• My code strictly adheres to the project guidelines (Standard library only, procedural code, clean spacing).
• I have verified that my files are placed in the correct directory.
• I have tested my changes thoroughly on my local machine.
• I have included interactive emojis and clean console/UI outputs.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

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[github-actions]

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