Constraint: Week (ISO week string)

[cursor]

Goal

Add a Week constraint — validate a string as a year and ISO week (like Assert\Week in Symfony), with week/year options if needed.

Reference

• Symfony: Symfony\Component\Validator\Constraints\Week.

Constraints

• No new dependencies — parse via time (ISO week); align behavior with Symfony documentation.

Scope

• Format parsing, week boundaries, tests for valid/invalid values.

Complexity

2 / 5.

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Migrated from Linear: IGO-36
Priority: High
Estimate: 2 points