✨ v3 theme: glass UI, landing layout, a11y, perf, print styles

Floating glass header with ⌘K search, landing homepage layout with
hero image and GitHub-stars CTA, background canvas with dissolving
heroes, burufugu colour scheme, movie-quote 404, taxonomy pills,
keyboard/ARIA accessibility across menus, search and tabs, idle-
loaded third-party scripts, and dedicated print styles.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

data/quotes404.json

@@ -0,0 +1,11 @@
+[
+  { "line": "You shall not pass!", "source": "The Fellowship of the Ring (2001)" },
+  { "line": "These aren't the droids you're looking for.", "source": "Star Wars (1977)" },
+  { "line": "Toto, I've a feeling we're not in Kansas anymore.", "source": "The Wizard of Oz (1939)" },
+  { "line": "Houston, we have a problem.", "source": "Apollo 13 (1995)" },
+  { "line": "Roads? Where we're going, we don't need roads.", "source": "Back to the Future (1985)" },
+  { "line": "It's just a flesh wound.", "source": "Monty Python and the Holy Grail (1975)" },
+  { "line": "I'll be back.", "source": "The Terminator (1984)" },
+  { "line": "You're gonna need a bigger boat.", "source": "Jaws (1975)" },
+  { "line": "E.T. phone home.", "source": "E.T. the Extra-Terrestrial (1982)" }
+]