perf: enable lite-yt-embed, optimize avatar, add cache headers

- YouTube embeds now use lite-youtube facade (loads iframe on click,
  ~800 KiB savings per page with embedded videos)
- Avatar resized from 1000x1000 to 400x400 (152 KiB → 39 KiB)
- lite-yt-embed.css max-width changed to 100% for responsive layout
- Removed unused Tailwind primary color palette from CSS bundle

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

css/lite-yt-embed.css

@@ -6,7 +6,7 @@ lite-youtube {
     background-position: center center;
     background-size: cover;
     cursor: pointer;
-    max-width: 720px;
+    max-width: 100%;
 }
 
 /* gradient */

eleventy.config.js

@@ -242,11 +242,18 @@ export default function (eleventyConfig) {
   });
 
   // Embed Everything - auto-embed YouTube, Vimeo, Bluesky, Mastodon, etc.
+  // YouTube uses lite-yt-embed facade: shows thumbnail + play button,
+  // only loads full iframe on click (~800 KiB savings).
+  // CSS/JS disabled here — already loaded in base.njk.
   eleventyConfig.addPlugin(embedEverything, {
     use: ["youtube", "vimeo", "twitter", "mastodon", "bluesky", "spotify", "soundcloud"],
     youtube: {
       options: {
-        lite: false,
+        lite: {
+          css: { enabled: false },
+          js: { enabled: false },
+          responsive: true,
+        },
         recommendSelfOnly: true,
       },
     },
@@ -266,7 +273,8 @@ export default function (eleventyConfig) {
   // Usage: {{ url | unfurlCard | safe }}
   eleventyConfig.addFilter("unfurlCard", getCachedCard);
 
-  // Custom transform to convert YouTube links to embeds
+  // Custom transform to convert YouTube links to lite-youtube embeds
+  // Catches bare YouTube links in Markdown that the embed plugin misses
   eleventyConfig.addTransform("youtube-link-to-embed", function (content, outputPath) {
     if (!outputPath || !outputPath.endsWith(".html")) {
       return content;
@@ -276,8 +284,8 @@ export default function (eleventyConfig) {
     const youtubePattern = /<a[^>]+href="https?:\/\/(?:www\.)?(?:youtube\.com\/watch\?v=|youtu\.be\/)([a-zA-Z0-9_-]+)[^"]*"[^>]*>(?:https?:\/\/)?(?:www\.)?[^<]*(?:youtube|youtu\.be)[^<]*<\/a>/gi;
 
     content = content.replace(youtubePattern, (match, videoId) => {
-      // Use standard YouTube iframe with exact oEmbed parameters
+      // Use lite-youtube facade — loads full iframe only on click
-      return `</p><div class="video-embed"><iframe width="560" height="315" src="https://www.youtube.com/embed/${videoId}?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen title="YouTube video"></iframe></div><p>`;
+      return `</p><div class="video-embed eleventy-plugin-youtube-embed"><lite-youtube videoid="${videoId}" style="background-image: url('https://i.ytimg.com/vi/${videoId}/hqdefault.jpg');"><div class="lty-playbtn"></div></lite-youtube></div><p>`;
     });
 
     // Clean up empty <p></p> tags created by the replacement

tailwind.config.js

@@ -41,20 +41,6 @@ export default {
           900: "#78350f",
           950: "#451a03",
         },
-        // Legacy — kept for compatibility, not used in templates
-        primary: {
-          50: "#eff6ff",
-          100: "#dbeafe",
-          200: "#bfdbfe",
-          300: "#93c5fd",
-          400: "#60a5fa",
-          500: "#3b82f6",
-          600: "#2563eb",
-          700: "#1d4ed8",
-          800: "#1e40af",
-          900: "#1e3a8a",
-          950: "#172554",
-        },
       },
       fontFamily: {
         sans: [