Feature: Lock quiz after first answer and show correct option (#740)

[narang24]

Fixes #740

Changes done:

• Locked quiz after first answer selection
• Disabled all other options after selection
• Automatically highlighted correct answer when a wrong option is chosen

Screenshots

After fix:

• Only one selection allowed
• Correct answer highlighted automatically

Preview Link(s):

(To be added after checks complete)

✅️ By submitting this PR, I have verified the following

• Checked to see if a similar PR has already been opened 🤔️
• Reviewed the contributing guidelines 🔍️
• Sample preview link added
• Tried squashing the commits into one

Summary by CodeRabbit

• New Features
  • Prevents multiple answer selections per question
  • Visually highlights selected answers
  • Reveals correct answer when an incorrect choice is made
  • Locks questions after selection to prevent changes

[coderabbitai]

Walkthrough

The quiz answer selection function is rewritten to prevent multiple answer selections and provide clearer feedback. A per-question locking mechanism is implemented using stored data to block further selections after the first answer is chosen. When an incorrect answer is selected, the correct answer is automatically displayed. All answer buttons within the question are disabled after selection by removing onclick handlers and disabling pointer events via CSS.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: locking the quiz after the first answer selection and displaying the correct option when wrong answers are chosen.
Linked Issues check	✅ Passed	The code changes implement all core requirements from issue #740: preventing multiple selections via per-question locking, showing selected answers with appropriate styling, and revealing correct answers when wrong options are chosen.
Out of Scope Changes check	✅ Passed	All changes are directly aligned with issue #740 requirements; no out-of-scope modifications were introduced.

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