Enhance documentation and admin UI: Add detailed implementation guidelines in CLAUDE.md, introduce a referrer index in README.md, and update admin UI translations for improved user experience. Update package dependencies for better functionality and performance.

README.md

@@ -11,6 +11,7 @@ A file-based headless CMS written in Rust. Content types are defined as JSON5 sc
 - **Optional SQLite**: Switch store via env – same API, different storage layer
 - **REST API**: Full CRUD endpoints, auto-generated per content type
 - **References & _resolve**: Reference fields as `{ _type, _slug }`; embed with `?_resolve=all`
+- **Referrer index**: Reverse index of who references which entry; file-based in `content/_referrers.json`; full reindex when file is missing; `GET /api/content/:type/:slug/referrers`
 - **Reusable partials**: `reusable` schemas and `useFields` for shared field groups (e.g. layout)
 - **Optional API auth**: Protect write access (POST/PUT/DELETE) with an API key via env
 - **Admin UI**: Next.js web interface for browsing collections, creating and editing content; manage types (list, create, edit, delete) with schema files and JSON Schema export updated on save
@@ -125,6 +126,10 @@ RUSTYCMS_STORE=sqlite cargo run
 RUSTYCMS_API_KEY=your-secret-token cargo run
 ```
 
+### Referrer index
+
+When not using `RUSTYCMS_ENVIRONMENTS`, the API maintains a **reverse index** of references: for each entry it knows which other entries reference it. This is stored as a single JSON file in the content directory: **`content/_referrers.json`**. On startup, if that file is missing, a full reindex is run over all collections and locales; on every create/update/delete the index is updated incrementally. Use **`GET /api/content/:type/:slug/referrers`** to list referrers (response: array of `{ collection, slug, field, locale? }`). Documented in Swagger UI and OpenAPI spec.
+
 ## Project structure
 
 ```
@@ -259,6 +264,8 @@ Add a `.json5` file under `types/`:
 | `fields`    | object   | Nested fields for object type                       |
 | `collection`| string   | Target collection for reference type                |
 | `useFields` | string   | For `type: "object"`: use fields from this schema (partial) |
+| `widget`    | string   | For `string`: `"textarea"` = multi-line; `"code"` = code editor with syntax highlighting (requires `codeLanguage`) |
+| `codeLanguage` | string | When `widget: "code"`: `"css"`, `"javascript"`, `"json"`, or `"html"` – used for highlighting and copy in admin UI |
 
 ### Field types
 
@@ -427,6 +434,7 @@ curl -X POST http://localhost:3000/api/content/product \
 | `DELETE` | `/api/schemas/:type`        | Delete type definition (Admin UI: Delete type) |
 | `GET`    | `/api/content/:type`        | List all entries               |
 | `GET`    | `/api/content/:type/:slug`  | Get single entry               |
+| `GET`    | `/api/content/:type/:slug/referrers` | List entries that reference this entry |
 | `POST`   | `/api/content/:type`        | Create entry                   |
 | `PUT`    | `/api/content/:type/:slug`  | Update entry                   |
 | `DELETE` | `/api/content/:type/:slug`  | Delete entry                   |