Add extended dashboard functionality with configurable widgets

immoreelrequested to merge
issue/piwik_pro-3575167:3575167-pinned-pages-in into 1.4.x
  • Add 15 new API fetch methods for analytics data: Traffic Sources, Geography, Downloads, Custom Events, Page Behavior, Browsers, Social Media, Performance, Sessions, Search Behavior, E-commerce, Goals, Content Tracking, Consent, Google Ads
    • Add corresponding API controller endpoints and routes
    • Add configurable widget settings (high/medium/lower priority groups)
    • Replace React app with vanilla JS dashboard implementation
    • Add Twig template with all widget sections
    • Add Chart.js integration with CDN fallback to local library
    • Add hook_library_info_alter for automatic local Chart.js detection
    • Update README with Chart.js installation documentation

Closes #3575167

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