Patch 1.3: smooth on every browser

This patch makes the site pleasant everywhere, even with an ad blocker or a less powerful computer.

• Ad blockers: some of them prevented pages from scrolling. That’s fixed, and a safety net unlocks the page if a script fails to load.
• Automatic light mode: if the page can’t keep up (for example Firefox without hardware acceleration), the site turns off its heaviest effects by itself (blurs, animated cursor, looping animations) to stay smooth.
• Firefox tip: Settings → General → Performance → tick “Use hardware acceleration when available”.