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/handbook/administration.en.md

@@ -0,0 +1,65 @@
+---
+title: Administration
+order: 13
+---
+
+# Administration
+
+The **Admin** area (`/admin`) is exclusively accessible to admins.
+Without the admin role, access is denied.
+
+> At the top right, the **Redundancy dashboard** button leads to the automatic
+> duplicate detection (see [Redundancy](/docs/handbook/redundanz)).
+
+## "Users" tab
+
+Management of local accounts.
+
+- **Add user:** username (required), password (at least 6 characters),
+  email (optional), **role** (User/Admin), **plan** (Free/Premium/Enterprise).
+- **Edit user:** set role, plan and (for local accounts) a new password.
+  For OIDC accounts, password management is offered in the identity provider
+  (e.g. Keycloak).
+- **Delete user:** permanently removes the account (not for your own account).
+
+API reference:
+[`POST /users`](/docs/reference/endpoints/users#createUser),
+[`PATCH /users/{id}`](/docs/reference/endpoints/users#updateUser),
+[`DELETE /users/{id}`](/docs/reference/endpoints/users#deleteUser).
+
+## "Tools" tab
+
+Central access to the tool catalog.
+
+- **Search** for tools.
+- View, edit or move individual tools to the trash.
+- **Bulk action:** select multiple tools and move them to the trash
+  (confirmation dialog; soft-deleted tools are removed from all public views
+  and can be restored or permanently deleted).
+
+## "Audit log" tab
+
+Chronological log of all creation, change and deletion operations
+(max. 100 entries): action, entity + ID, timestamp, executing person and
+changed fields.
+
+API reference: [`GET /audit-logs`](/docs/reference/endpoints/audit#listAuditLogs).
+
+## "System" tab
+
+Version information of the running instance:
+
+- **Version** (e.g. `v0.8.1`),
+- **Commit** (7-digit SHA, linked to the repository),
+- **Build date**,
+- **Trash retention** ("N days" or "Forever").
+
+## Tool links (Admin)
+
+On the detail page of a tool you can manage **links** as an admin
+(own/"manual" as well as automatically detected ones):
+
+- **Link tool:** dialog with tool ID, **relationship type**
+  (Similar / Replaces / Superseded by) and optional notes.
+- Relationship types are displayed as badges on the detail page.
+- Manual links can be removed again via the trash icon.