🔒 Fix loose type comparison vulnerability in Insee validation

[ronanguilloux]

🎯 What: The IsoCodes\Insee::validate() method used a loose type comparison (!=) to verify the calculated checksum ($clef) against the provided checksum ($return['clef']).

⚠️ Risk: Loose type comparisons in PHP can lead to type juggling vulnerabilities. An attacker could potentially bypass the validation check by providing unexpected inputs (e.g., '0x44' or ' 44') that evaluate to true under loose comparison rules (!=) but are not strictly identical, potentially leading to security issues.

🛡️ Solution: Updated the comparison to use strict inequality (!==). Since $clef is an integer/float and $return['clef'] is a string that might contain leading zeros (e.g. '01'), the calculated $clef is now formatted using sprintf('%02d', $clef) to match the 2-digit string format expected from the regular expression. Both values are explicitly cast to strings before comparison to prevent any type coercion. Added test cases to ensure type-juggling prevention correctly invalidates malicious inputs.

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PR created automatically by Jules for task 17023328866465612220 started by @ronanguilloux

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