feat(landing): static marketing page for Vercel

Single self-contained index.html under landing/ — no build step.
Product design tokens (dark theme, Geist + Geist Mono self-hosted,
#3b82f6 accent), hero with framed board screenshot, feature bento,
screenshots strip, install commands with copy buttons.

Deployed as Vercel project "dash" -> https://dash.vercel.app

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

AGENTS.md

@@ -9,6 +9,7 @@ Optional auth (off by default), no YAML. See `ROADMAP.md` (canonical) and
 - `apps/frontend` — React 18 + Vite + TS strict + Tailwind v4 + shadcn/ui
 - `apps/backend` — Go + Gin + zap, CGO-free, SQLite via `modernc.org/sqlite`
 - `packages/api-client` — generated TS client; `openapi.yaml` at repo root is the contract
+- `landing/` — static marketing page, deployed to Vercel; no build step, plain HTML/CSS/JS
 - `infra/` — Dockerfile (multi-stage, one image)
 - `tools/oxlint/anti-slop` — vendored lint plugin (do not extend casually)
 - `data/` — runtime SQLite + uploaded icons (gitignored)