🎨 Palette: Add accessible labels to ecosystem buttons

[google-labs-jules]

This PR improves accessibility by adding descriptive aria-label attributes to interactive elements in EcosystemPage and HomePage. Specifically:

• Buttons that previously just said "GitHub", "npm", "PyPI", or "Source" now include the package name (e.g., "View [Package Name] source on GitHub").
• The search input and filter groups in the Ecosystem page now have proper labels.

These changes ensure screen reader users can distinguish between multiple identical buttons in lists and understand the purpose of form controls.

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PR created automatically by Jules for task 828936413953970168 started by @jbdevprimary

[google-labs-jules]

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