Enhance SEO, Analytics, and Internal Linking

[Vaishnav88sk]

Description

This PR introduces several frontend enhancements to improve the site's SEO, track user conversions, and resolve existing Javascript console errors.

• Analytics Tracking: Added safe gtag onclick events to primary "Get Started" and "Try Microcks" call-to-action buttons across the homepage and navigation headers.
  (Example: gtag('event', 'click', {'event_category': 'conversion'}) will now populate the Google Analytics 4 (GA4) dashboard "Events" report, allowing us to track exact button conversion rates).
• Core Web Vitals: Set loading="lazy" as the default behavior for all images rendered via the figure.html shortcode to improve page load speed.
• Internal Linking (SEO): Implemented a dynamic "Related Content" section at the bottom of both Blog and Documentation pages using robust Section-based Hugo filtering.
• Javascript Stability: Fixed Uncaught TypeError crashes in bootstrap.js and script.js by adding existence checks (if (nav) and if (searchModalEl)) so scripts degrade gracefully on pages that do not contain certain UI elements.
• Build Optimization: Converted standard HTML comments around partials in single.html to native Hugo comments ({{/* */}}) to prevent unnecessary server-side template execution.

Related issue(s)

Part of #209