feat(search): product search component + navbar triggers

Adds a client-side fuzzy product search to the design system:

- `src/api/products.js`: fixture catalogue (22 products across the Kaiser
  Natron, Holste, Gazelle, Grüne Tante and Linda ranges) plus a scored,
  diacritic-folded search (ß→ss, ä→ae, NFKD) with weighted fields
  (title 5, brand/keywords 3, size/category 2, id 1) and prefix bonus.
- `Search.vue`: tone-driven (brand/paper/cream) full-screen overlay on
  mobile, centered modal on md+. Auto-focus, arrow-key nav, Enter/Esc,
  suggested-products empty state, keyboard-hint footer on desktop, safe-
  area aware, scroll-locks the document while open.
- Navbar now hosts two triggers: a pill-shaped "Search products"
  lookalike (desktop, in the same LanguageSwitcher-style container) and
  a green/accent shadow-sm floating button bottom-left on mobile. Both
  open the same overlay.
- HomePage feeds the products list into Navbar.
- Design-system showcase (`/design/search`) with live demo + canned
  result preview + usage snippet. Sidebar + mobile bottom-nav entries
  and DE/EN i18n added.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

dist/index.html

@@ -12,7 +12,7 @@
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       rel="stylesheet"
     />
-    <script type="module" crossorigin src="/assets/index-BbWJ9mTE.js"></script>
+    <script type="module" crossorigin src="/assets/index-DnYgINTf.js"></script>
     <link rel="modulepreload" crossorigin href="/assets/_plugin-vue_export-helper-CXTkFu_Z.js">
     <link rel="modulepreload" crossorigin href="/assets/runtime-core.esm-bundler-CjdnoyKJ.js">
     <link rel="modulepreload" crossorigin href="/assets/runtime-dom.esm-bundler-CDZvOKZN.js">