fix(contributions): auto-redirect vers la concention collective quand celle-ci a été sauvegardée dans le header

[maxgfr]

fix #7182

[revu-bot]

PR Review: Auto-redirect to collective agreement page from header

This PR implements auto-redirection to a CC-specific contribution page when a collective agreement has been previously saved in localStorage (via the site header). The implementation is generally clean and well-tested, but there are a few issues worth addressing.

File	Lines	Severity	Issue
ContributionGeneric.tsx	58–71	CRITICAL	Missing redirect loop guard — unpublished CC can cause infinite redirect
ContributionGeneric.tsx	58–71	IMPORTANT	useEffect with empty deps array accesses stale slug/contribution via closure
ContributionGeneric.tsx	63–65	IMPORTANT	Hardcoded slug string is a fragile magic constant
contributions.test.tsx	308–385	IMPORTANT	Tests don't clear localStorage between cases — state leaks between tests

[revu-bot]

[IMPORTANT] Hardcoded slug string is a fragile magic constant

• If the slug for "congés pour événements familiaux" ever changes (rename, typo fix, etc.), this silent branch will silently stop working with no compile-time error.
• The special-casing logic is duplicated here and likely elsewhere in the codebase.

Proposed fix: Extract this to a named constant (or derive it from the contribution data) so the intent is clear and the value is maintained in one place.

Suggested change

	const targetUrl =
	slug === "les-conges-pour-evenements-familiaux"
	? `/contribution/${slug}/${storedAgreement.slug || storedAgreement.num}`
	: `/contribution/${storedAgreement.num}-${slug}`;
	const CONGES_FAMILIAUX_SLUG = "les-conges-pour-evenements-familiaux";
	const targetUrl =
	slug === CONGES_FAMILIAUX_SLUG
	? `/contribution/${slug}/${storedAgreement.slug || storedAgreement.num}`
	: `/contribution/${storedAgreement.num}-${slug}`;

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[tokenbureau]

🎉 Deployment for commit 41a9201 :

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