Restructure into apps/* monorepo and add marketing website

[Gift-Stack]

What

Three commits:

1. refactor: move desktop app to apps/desktop monorepo layout — promotes the repo to a proper apps/* + packages/* layout. The desktop app moves app/ → apps/desktop/ (via git mv, full history preserved), and every path reference is updated.
2. feat: add marketing website under apps/website — a Next.js 16 + Tailwind 4 landing page for Pontoon.
3. fix(desktop): resolve repo root three levels up in build.rs — the move broke the Tauri sidecar build (see Verification).

Restructure details

File	Change
pnpm-workspace.yaml	"app" → "apps/*"
scripts/build-sidecar.mjs	sidecar output → apps/desktop/src-tauri/binaries
.github/workflows/release.yml	projectPath + rust-cache workspaces → apps/desktop
.gitignore	tauri ignore rules → apps/desktop/…; added .next, *.tsbuildinfo
turbo.json	build outputs now include .next/** (minus cache)
apps/desktop/src-tauri/build.rs	repo root now resolved three levels up (was two); rerun-if-changed paths ../../ → ../../../
README.md	structure tree + doc paths

I kept the package name @pontoon/app (referenced by --filter, so pnpm dev, desktop:dev, and the release workflow keep working). Happy to rename to @pontoon/desktop in a follow-up.

Website details

@pontoon/website, dark-first single-page landing. Reuses the product's exact design tokens (charcoal + the two pontoon greens, ported from apps/desktop/src/styles.css) so the site and app read as one product. Archivo + JetBrains Mono; the hero centrepiece is a live in-code transaction-tree inspector mock. Sections: hero → features → how-it-works → panels → CTA → footer. Runs with pnpm --filter @pontoon/website dev (port 3100). Passes a WCAG pass (faint-text contrast to AA, CTA touch targets ≥44px, visible focus states, reduced-motion).

Verification

• pnpm install --frozen-lockfile resolves the new apps/* workspace.
• pnpm tsc (turbo across desktop + website + bridge) passes.
• Website: clean production build (next build, static prerender); typechecks cold; verified in-browser at 375 / 390 / 1440px, no console errors, no horizontal overflow.
• Desktop dev (pnpm dev): Vite serves the app from apps/desktop (5173) and the bridge runs from packages/bridge (37631); the app UI renders and shows "Bridge connected", Status Healthy, seeded treasuries.
• Desktop build (pnpm desktop:build): the move broke build.rs (it resolved the repo root two levels up, so the sidecar step looked in apps/scripts/ instead of scripts/). Fixed in commit 3. After the fix, a clean build compiles the Rust app in release and produces Pontoon.app (arm64, dev.entrypoint.pontoon v0.1.0) with the pontoon-bridge sidecar embedded.

Note

The bundle_dmg.sh step fails in a headless session (it drives Finder via AppleScript to style the disk image); the .app itself builds fine, and the release workflow runs on real macos-latest runners where DMG bundling works. Not a code issue and not changed here.