feat: add Catppuccin file icons

[isWittHere]

Summary

Replace the hand-written monochrome file and folder icons with a
selected set of official Catppuccin Icons.

Light mode uses Latte assets and dark mode uses Mocha assets.

Changes

• Replace the SVG JSX in components/FileIcons.tsx with a shared
  Catppuccin icon resolver.
• Select the icon flavor through the existing html.dark state, so
  the correct assets are used before React hydration.
• Add only the SVGs used by the current resolver, together with the
  upstream MIT license and source-version documentation.
• Preserve existing resolver call sites and extension mappings.
• Use dedicated upstream icons for npm/Bun lockfiles, Next.js config,
  and ESLint config files.

Verification

• node_modules/.bin/tsc --noEmit
• npm run lint
• git diff --check
• Manually checked Explorer icons, open/closed folders, file tabs,
  changed-file rows, and @ path completion in light and dark themes.

Preview