perf: address PageSpeed Insights issues (CLS, contrast, touch targets, JS minification)

- Reserve sidebar min-height on desktop to prevent CLS from Alpine.js hydration
- Defer lite-yt-embed.css with media="print" onload pattern
- Add terser JS minification in eleventy.after build hook
- Increase touch target sizing for category pills, facepile avatars, nav items
- Fix text-surface-400 contrast ratio (3.05:1 → 6.23:1) across 20 instances

Confab-Link: http://localhost:8080/sessions/edb1b7b0-da66-4486-bd9c-d1cfa7553b88

css/critical.css

@@ -45,6 +45,8 @@ main.container{padding-top:1.5rem;padding-bottom:1.5rem}
 .layout-with-sidebar{display:grid;grid-template-columns:1fr;gap:1.5rem}
 @media(min-width:1024px){.layout-with-sidebar{grid-template-columns:2fr 1fr;gap:2rem}}
 .main-content{min-width:0;overflow-x:hidden}
+/* Reserve sidebar space on desktop to prevent CLS when Alpine.js hydrates collapsible widgets */
+@media(min-width:1024px){.sidebar{min-height:600px}}
 
 /* Basic typography — prevent FOUT */
 h1,h2,h3,h4{margin:0;line-height:1.25}