fix(seo): resolve ahrefs site audit issues and fix android pwa icons

[kascit]

Summary

This PR addresses all 36 issues flagged in the Ahrefs Site Audit (Project ID 9650520) along with Android PWA favicon & manifest resolution and cross-platform / cross-architecture pipeline reliability improvements.

Key Changes

1. Image File Size Too Large (9 errors):
   • Fixed ImageMagick child process timeout threshold in scripts/lib/shared.js from 1,000ms to 60,000ms, enabling responsive WebP variants (400w, 800w, 1200w, 1600w) to generate cleanly for all 81 images.
2. Broken JavaScript (3+1 errors):
   • Configured stable ESM loader generation in scripts/fingerprint-assets.js at public/js/shell.js forwarding to public/js/core/shell.<hash>.js.
3. Orphan Page (1 error):
   • Added internal footer navigation link to content/design/_index.md and included a dedicated card on content/links/_index.md.
4. Links to 302/301 Redirects (134 warnings):
   • Fixed tasks.dhanur.me endpoint to https://tasks.dhanur.me/app/index.html in data/projects.json and templates/macros/apps.html.
   • Normalized trailing slashes across internal project links (pulse, auth, up, linkr).
   • Fixed external redirect URLs (Kubernetes docs, Spring Boot projects, Discord invite).
5. Short Meta Descriptions (123 warnings):
   • Enriched dynamic taxonomy description generators in templates/base.html (130–155 chars).
   • Enriched descriptions in config.toml and all section/content markdown pages to the 120–150 character range.
   • Fixed meta description resolution in templates/macros/head.html.
6. Title & Word Count Issues:
   • Shortened content/blog/writing-documentation.md title to 52 characters.
   • Added SEO metadata, outgoing links, and noindex headers to utility pages (open-file, share-target, handler).
7. Duplicate Pages & Non-Canonical Sitemap Entries:
   • Excluded redirect stubs and noindex utilities from scripts/generate-sitemap.js.
   • Injected noindex, follow, canonical links, and back-navigation into redirect stubs in scripts/clean-pagination-redirects.js.
8. Android PWA Favicon & Orientation:
   • Maintained "orientation": "portrait" per explicit requirement.
   • Cleaned query params from icon paths in static/icons/site.webmanifest and updated Apple touch icon fallback in config.toml / templates/macros/head.html.
9. Cross-Platform Compatibility:
   • Standardized shell scripts in justfile to avoid platform-specific sed in-place flags and non-portable bash arithmetic.

Verification

• just quality passed 100% (JS lint, CSS lint, XML/XSL validation, icon asset validation, and zola check with 30 pages / 0 orphans).
• just build completed with 0 errors across 81 responsive images (401 WebP variants), shell ESM bundling, and asset fingerprinting.
• Automated SEO audit script verified 0 audit errors across all 133 generated HTML files in public/.

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