feat: add interactive Game of Life cellular automata page

[arc-butler]

What

Adds an interactive Game of Life (Conway's cellular automata) simulation as a new page on the site, accessible from the navbar dropdown.

Why

Arnav's about page lists cellular automata as a core interest. This puts a living, interactive demonstration of that interest directly on the site — it's a conversation starter that's also genuinely fun to play with.

What makes it weird

• The initial seed pattern is derived from Arnav's actual travel coordinates — lat/lng from the travel map are mapped to grid cells, so every trip he's taken becomes a live cell at startup
• Blog post count, project count, and travel count are embedded in the seed data (though not all visually displayed — they affect the organic random fill density)
• Cell brightness decays with age: newborn cells glow, veterans fade — giving the simulation a living-organism feel
• Toroidal (wrap-around) grid so patterns can migrate across edges
• Dark/light mode aware — reads CSS custom properties from the theme system and re-draws on theme toggle
• Keyboard shortcuts: Space (toggle), C (clear), R (randomize) — plus click to toggle individual cells

What's sensible

• Pure frontend: Canvas API, zero dependencies, one JS file
• Conway's Game of Life is a computer science classic — no gimmick value, just a well-executed interactive demo
• Follows existing al-folio conventions: Jekyll page with embedded Liquid data (same pattern as the Leaflet travel map in _layouts/leaflet_map.liquid)
• Reuses the site's CSS custom properties for theming
• Adds to the existing navbar dropdown (bookshelf > life > divider > blog)

Files changed

• _pages/life.md (new) — Jekyll page with embedded Liquid data and canvas container
• assets/js/game-of-life.js (new) — Full Game of Life engine: grid, rendering, controls, seeding
• _pages/dropdown.md (modified) — Added "life" link to the dropdown menu