Address 404s

[tunetheweb]

Part of #452

• Log errors better by including request URL.
• Add <link rel="apple-touch-icon" (often causes a lot of 404s if not present).
• Fix bad links in PWA, Security and Resource Hints chapters.

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 42.4%, saving 13.02 KB

Filename	Before	After	Improvement
src/static/images/apple-touch-icon-160x160.png	15.36 KB	8.85 KB	-42.4%
src/static/images/apple-touch-icon.png	15.36 KB	8.85 KB	-42.4%

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