feat: initial @unom/app-ui — shared app-level blocks, starting with the footer

Composite UI blocks shared across the unom/punktfunk apps, one layer up from
@unom/ui (primitives). Follows the @played/app-ui pattern: per-block subpath
exports, tsdown ESM+dts build, themed through @unom/style semantic tokens.

The ./footer block exports a presentational FooterView (link sections, socials,
tagline) with a resolveHref hook so the docs can rebase root-relative links onto
the marketing-site origin. Both the punktfunk marketing site and docs render it,
so the footer no longer drifts between hand-mirrored copies.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

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+# @unom/app-ui
+
+Composite, app-level UI blocks shared across the unom/punktfunk apps (the
+marketing site and the docs site). One layer up from
+[`@unom/ui`](https://git.unom.io/unom/-/packages), which is primitives only —
+this package hosts larger blocks/sections that more than one app renders, so
+they stay in sync instead of being hand-mirrored per repo.
+
+Components are themed entirely through `@unom/style`'s semantic tokens
+(`neutral-accent`, `main`, …). Each consumer maps those tokens to its own
+surfaces (the marketing site's blue theme, the docs' Fumadocs violet/dark
+chrome), so the markup is identical while each site keeps its palette.
+
+## Subpath exports
+
+- `@unom/app-ui/footer` — `<FooterView>`: the punktfunk footer (link sections,
+  socials, tagline). Presentational; data fetching stays in each app's route
+  loader. Pass `resolveHref` to rebase root-relative links onto another origin
+  (the docs do this so footer links target the marketing site).
+
+```tsx
+import { FooterView } from "@unom/app-ui/footer";
+
+<FooterView
+  sections={footer?.sections}
+  tagline={footer?.tagline}
+  socials={footer?.socials}
+  socialsLabel={m.footer_socials()}
+/>;
+```
+
+## Develop
+
+```sh
+bun install
+bun run build      # tsdown → dist/ (esm + d.ts)
+bun run typecheck
+```
+
+`dist/` is published (not committed). Releases go to the private Gitea npm
+registry under the `@unom` scope via `bun publish`.