feat(search): tone-aware product search with mobile + desktop triggers

Introduces:
- src/api/fixtures/products.js + src/api/index.js — placeholder catalog
  (24 products across Kaiser-Natron / Holste / Gazelle / Grüne Tante /
  Linda) so search has real data. Same shape the backend will return.
- Search.vue — Teleported dialog. Token-scored, diacritics-folded, ß→ss
  normalized so German terms still match when users type ASCII. Keyboard
  navigation (↑/↓/Enter/Esc), autofocus on open, scroll-lock. Full-screen
  on mobile, centered command-palette modal on md+. Tone prop defaults
  to 'brand' so the overlay reads as the site's primary affordance
  (green), with 'paper' and 'cream' variants available.
- SearchSection.vue + ds-search route + sidebar entry.
- DE + EN strings for the overlay and the showcase.

Navbar wires the triggers: desktop search button sits left of the
LanguageSwitcher in the right cluster; mobile gets a matching bottom-
left floating button (cream surface, safe-area padded) that mirrors the
existing bottom-right cart/menu cluster. The Search overlay is mounted
inside Navbar with the default catalog, so every page that renders a
Navbar gets search for free. Selected products bubble up as a
@select event for navigation handling.

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

src/router/index.js

@@ -39,6 +39,7 @@ const routes = [
       { path: 'navbar', name: 'ds-navbar', component: () => import('@/pages/design/NavbarSection.vue') },
       { path: 'language', name: 'ds-language', component: () => import('@/pages/design/LanguageSwitcherSection.vue') },
       { path: 'icons', name: 'ds-icons', component: () => import('@/pages/design/IconsSection.vue') },
+      { path: 'search', name: 'ds-search', component: () => import('@/pages/design/SearchSection.vue') },
     ],
   },
 ]