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.en.md

@@ -0,0 +1,51 @@
+
+# Welcome to toolr
+
+toolr is a platform for **discovering, rating and comparing development
+tools**. Users maintain a shared catalog of tools, submit ratings
+(usefulness & usability) and use statistics to make the right choice.
+
+## What can you do with toolr?
+
+| Function | Description | Visibility |
+| --- | --- | --- |
+| **Browse tools** | Filter, sort and search the catalog | Everyone |
+| **Create a tool** | Add a new tool with description, category, features & tags | Logged in |
+| **Edit/delete tools** | Maintain your own tools (creator or admin) | Logged in |
+| **Rate** | Submit usefulness & usability (1–5) plus a comment | Logged in |
+| **Watchlist** | Save tools as favorites | Premium |
+| **Compare** | View tools side by side | Premium |
+| **Record costs** | Enter license and cost models per tool | Premium |
+| **Analytics** | Statistics, top tools, distributions | Everyone |
+| **Trash** | Restore soft-deleted tools or delete them permanently | Premium |
+| **Admin** | User management, audit log, system information | Admin |
+| **Redundancy detection** | Automatic duplicate detection | Admin |
+
+## How this documentation is organized
+
+- **User Guide** (these pages): step-by-step instructions for all
+  functions — from the [Getting Started](/docs/handbook/getting-started) to
+  [Administration](/docs/handbook/administration).
+- **API Reference**: automatically generated from the OpenAPI specification —
+  all [endpoints](/docs/reference/endpoints/tools) and
+  [data fields](/docs/reference/schemas/toolinput) of the current version.
+- **Release Notes**: what is new in each [version](/docs/releases/v0.8.1).
+
+## Getting started
+
+The fastest way:
+
+1. **Sign in** — without an account you can only browse
+   (see [Getting Started](/docs/handbook/getting-started#1-anmelden)).
+2. **Find tools** — search, filters and sorting in the
+   [Browse tools](/docs/handbook/tools-finden) section.
+3. **Create a tool** — via "Add tool"
+   ([guide](/docs/handbook/tool-anlegen)).
+4. **Rate** — on the detail page of a tool
+   ([guide](/docs/handbook/bewerten)).
+
+## Contact & source code
+
+The source code is available at
+[git.kubebase.de/admin/tool-evaluator](https://git.kubebase.de/admin/tool-evaluator) —
+you can reach it at any time via the repository icon in the top right corner.