fix(calculator): require explicit data argument and remove fallback s…

[sanskar0627]

Fix #166
This PR updates the calculator API to require explicit input data when computing IQB scores and removes the implicit fallback sample behavior.

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Problem

calculate_iqb_score previously accepted missing data and silently used an internal sample payload.

This could:

• Hide caller mistakes
• Produce scores from placeholder values
• Conflict with the intent to remove default sample-based scoring

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What Changed

calculator.py

• calculate_iqb_score now requires the data argument
• Removed the internal fallback sample data block
• Kept print_details behavior unchanged (out of scope for this PR)

calculator_test.py

• Tests now pass explicit sample input instead of relying on implicit defaults
• Updated related test wording for accuracy

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Why This Is Important

• Makes the API contract explicit and safer
• Prevents accidental scoring with non-production placeholder data
• Improves correctness
• Surfaces integration failures earlier

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All Test Passed

[bassosimone]

After listing our project for GSoC, we received a large amount of pull requests across several repositories. We are dealing with the backlog, but this would take time. We will get back to this pull request eventually. In the meanwhile, if you are a GSoC applicant, please read our updated GSoC policy: https://github.com/m-lab/gsoc/.