feat(i18n): full app + docs localization (de/en)

- translate remaining pages/components (admin, analytics, redundancy,
  trash, compare, browse, watchlist, admin tools tab, category combobox,
  theme toggle, tool preview card, tool-new/edit) to t() calls
- locales: 453 keys each, parity verified
- docs: bilingual handbook + release notes via *.en.md variants,
  language-aware docs.tsx (markdown paths, nav titles, search index),
  LanguageSwitcher in docs header
- generate-docs: emit per-locale handbook/release/search output,
  localized index.json fields (fileEn/titleEn), en-aware snapshots

docs/releases/v0.8.1/handbook/index.json

@@ -3,102 +3,136 @@
     "slug": "index",
     "file": "index.md",
     "title": "Überblick",
-    "order": 1
+    "order": 1,
+    "fileEn": "index.en.md",
+    "titleEn": "Overview"
   },
   {
     "slug": "getting-started",
     "file": "getting-started.md",
     "title": "Erste Schritte",
-    "order": 2
+    "order": 2,
+    "fileEn": "getting-started.en.md",
+    "titleEn": "Getting Started"
   },
   {
     "slug": "konto",
     "file": "konto.md",
     "title": "Anmelden & Konto",
-    "order": 3
+    "order": 3,
+    "fileEn": "konto.en.md",
+    "titleEn": "Login & Account"
   },
   {
     "slug": "tools-finden",
     "file": "tools-finden.md",
     "title": "Tools finden & durchsuchen",
-    "order": 4
+    "order": 4,
+    "fileEn": "tools-finden.en.md",
+    "titleEn": "Find & browse tools"
   },
   {
     "slug": "tool-anlegen",
     "file": "tool-anlegen.md",
     "title": "Tool anlegen",
-    "order": 5
+    "order": 5,
+    "fileEn": "tool-anlegen.en.md",
+    "titleEn": "Create a tool"
   },
   {
     "slug": "tool-bearbeiten",
     "file": "tool-bearbeiten.md",
     "title": "Tool bearbeiten & löschen",
-    "order": 6
+    "order": 6,
+    "fileEn": "tool-bearbeiten.en.md",
+    "titleEn": "Edit & delete tools"
   },
   {
     "slug": "bewerten",
     "file": "bewerten.md",
     "title": "Bewerten",
-    "order": 7
+    "order": 7,
+    "fileEn": "bewerten.en.md",
+    "titleEn": "Rating"
   },
   {
     "slug": "watchlist",
     "file": "watchlist.md",
     "title": "Watchlist",
-    "order": 8
+    "order": 8,
+    "fileEn": "watchlist.en.md",
+    "titleEn": "Watchlist"
   },
   {
     "slug": "vergleichen",
     "file": "vergleichen.md",
     "title": "Vergleichen",
-    "order": 9
+    "order": 9,
+    "fileEn": "vergleichen.en.md",
+    "titleEn": "Compare"
   },
   {
     "slug": "analytics",
     "file": "analytics.md",
     "title": "Analytics",
-    "order": 10
+    "order": 10,
+    "fileEn": "analytics.en.md",
+    "titleEn": "Analytics"
   },
   {
     "slug": "plaene",
     "file": "plaene.md",
     "title": "Pläne & Berechtigungen",
-    "order": 11
+    "order": 11,
+    "fileEn": "plaene.en.md",
+    "titleEn": "Plans & Permissions"
   },
   {
     "slug": "kosten",
     "file": "kosten.md",
     "title": "Kosten erfassen",
-    "order": 12
+    "order": 12,
+    "fileEn": "kosten.en.md",
+    "titleEn": "Recording Costs"
   },
   {
     "slug": "administration",
     "file": "administration.md",
     "title": "Administration",
-    "order": 13
+    "order": 13,
+    "fileEn": "administration.en.md",
+    "titleEn": "Administration"
   },
   {
     "slug": "redundanz",
     "file": "redundanz.md",
     "title": "Redundanz-Dashboard",
-    "order": 14
+    "order": 14,
+    "fileEn": "redundanz.en.md",
+    "titleEn": "Redundancy dashboard"
   },
   {
     "slug": "papierkorb",
     "file": "papierkorb.md",
     "title": "Papierkorb",
-    "order": 15
+    "order": 15,
+    "fileEn": "papierkorb.en.md",
+    "titleEn": "Trash"
   },
   {
     "slug": "tastatur",
     "file": "tastatur.md",
     "title": "Tastenkürzel & Kommandopalette",
-    "order": 16
+    "order": 16,
+    "fileEn": "tastatur.en.md",
+    "titleEn": "Keyboard shortcuts & command palette"
   },
   {
     "slug": "datenmodell",
     "file": "datenmodell.md",
     "title": "Datenmodell",
-    "order": 17
+    "order": 17,
+    "fileEn": "datenmodell.en.md",
+    "titleEn": "Data model"
   }
 ]