feat: add syntax highlighting for code blocks

Integrates @11ty/eleventy-plugin-syntaxhighlight (PrismJS) for
build-time syntax highlighting of fenced code blocks. Includes
a custom GitHub-inspired theme with dark mode support (.dark class).

All existing articles with triple-backtick code blocks will
automatically get highlighting on next Eleventy rebuild.

Also fixes overflow-x: hidden on .prose/.e-content that was
clipping scrollable code blocks — changed to overflow-x: clip.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -10,23 +10,24 @@
   },
   "dependencies": {
     "@11ty/eleventy": "^3.0.0",
-    "html-minifier-terser": "^7.0.0",
-    "markdown-it": "^14.0.0",
     "@11ty/eleventy-fetch": "^4.0.1",
     "@11ty/eleventy-img": "^6.0.0",
     "@11ty/eleventy-plugin-rss": "^2.0.2",
+    "@11ty/eleventy-plugin-syntaxhighlight": "^5.0.2",
+    "@atproto/api": "^0.12.0",
     "@chrisburnell/eleventy-cache-webmentions": "^2.2.7",
     "@quasibit/eleventy-plugin-sitemap": "^2.2.0",
-    "@atproto/api": "^0.12.0",
     "eleventy-plugin-embed-everything": "^1.21.0",
-    "rss-parser": "^3.13.0",
-    "pagefind": "^1.3.0"
+    "html-minifier-terser": "^7.0.0",
+    "markdown-it": "^14.0.0",
+    "pagefind": "^1.3.0",
+    "rss-parser": "^3.13.0"
   },
   "devDependencies": {
-    "tailwindcss": "^3.4.0",
+    "@tailwindcss/typography": "^0.5.0",
+    "autoprefixer": "^10.4.0",
     "postcss": "^8.4.0",
     "postcss-cli": "^11.0.0",
-    "autoprefixer": "^10.4.0",
-    "@tailwindcss/typography": "^0.5.0"
+    "tailwindcss": "^3.4.0"
   }
 }