Feat/filter controls structured data

[lamborghini21]

Summary

Implements Structured Data (JSON-LD) for Filter Controls to improve SEO and accessibility.

Changes

• Add structuredDataUtils.ts with JSON-LD generation utilities (schema.org compliant)
• Add StructuredDataScript.tsx React component for rendering structured data
• Update FilterSidebar.tsx — structured data for search filters (difficulty, duration, price, topics)
• Update DashboardFilters.tsx — structured data for dashboard filters (time range, metric, categories)
• Update FacetedFilterSystem.tsx — structured data for faceted filters (content type, rating, price)
• Add unit tests in structuredDataUtils.test.ts
• Add STRUCTURED_DATA_IMPLEMENTATION.md documentation

Acceptance Criteria

• Filter Controls properly implements Structured Data
• All related tests pass
• No regression in existing functionality
• Code follows project coding standards
• Documentation updated
• Minimal performance impact (useMemo used throughout)
• Accessibility guidelines followed
• Security considerations addressed (XSS prevention via JSON validation)

Closes #380

[drips-wave]

@lamborghini21 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[RUKAYAT-CODER]

Thank you for contributing to the project.