Add a help link to legacy DC

[eyeseast]

Open to suggestions for a different icon or text here.

This is the last piece of #809

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	30.83%	6675 / 21645
🔵	Statements	30.83%	6675 / 21645
🔵	Functions	49.63%	273 / 550
🔵	Branches	75.43%	1007 / 1335

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/lib/components/navigation/HelpMenu.svelte	0%	0%	0%	0%	1-92

Generated in workflow #744 for commit 753b722 by the Vitest Coverage Report Action

[netlify]

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Lighthouse	1 paths audited Performance: 57 Accessibility: 85 Best Practices: 92 SEO: 91 PWA: - View the detailed breakdown and full score reports

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[allanlasser]

LGTM—just need to put the icon the start slot for alignment with other menu items.