🎨 Palette: Add skip to main content links

[0m364]

💡 What: Added a "Skip to main content" link as the first focusable element on all HTML pages (index.html, products.html, concepts.html, contact.html).

🎯 Why: To allow keyboard-only users and screen reader users to easily bypass repetitive top-level navigation links and jump directly to the main content.

📸 Before/After: Before, pressing Tab navigated through all header links. Now, the first Tab press reveals a prominent "Skip to main content" link.

♿ Accessibility: This is a fundamental WCAG requirement for bypassing blocks of content (WCAG 2.4.1). Added id="main-content" to all <main> tags.

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PR created automatically by Jules for task 5068917565907149609 started by @0m364

[google-labs-jules]

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