fix: use consistent 2 d.p. rounding in answer checks (closes #179)

[jindal-sneha]

Closes #179

Problem

Answer validation and displayed answers used different rounding rules:

• TEN-MATH-022 (Mensuration): 46.10 was accepted but feedback showed 46.08, because the check allowed a tolerance of 0.5.
• TEN-MATH-019 (Speed/Distance/Time): the wording said "to 2 d.p. if needed" while the check rejected 43 and expected 43.13.

Changes

• server/routes/geometry.js (mensur check): compare answers rounded to 2 d.p. instead of a 0.5 tolerance.
• server/routes/misc.js (cyclist average-speed question): clarified wording to "Give your answer correct to 2 decimal places." and changed the check to compare at 2 d.p. instead of a 0.05 tolerance.

Testing

• Verified the comparison logic with Node: 46.10 vs 46.08 is rejected, 46.08 is accepted; 43 vs 43.13 is rejected, 43.13 is accepted.
• Did not run the full app end to end.

[github-actions]

✅ Parikshak — all automated checks pass

• ✅ Linked to open issue Validator and displayed answer use different rounding rules (TEN-MATH-019, 022) #179 — Validator and displayed answer use different rounding rules (TEN-MATH-019, 022)
• ✅ No merge conflict

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