feat: Implement collection deletion and loading spinners

- Add API endpoint and handler to delete collections
- Introduce LoadingSpinner component for async operations
- Show loading spinners during file loading and preview rendering
- Enhance modal accessibility by removing aria-hidden attribute
- Refactor delete functionality to distinguish between collections and files/folders
- Remove unused collection definitions from config

collections/documents/docusaurus.md

@@ -0,0 +1,44 @@
+## Using Docusaurus
+
+Once you've set up Hero, you can use it to develop, manage and publish Docusaurus websites.
+
+## Launch the Hero Website
+
+To start a Hero Docusaurus website in development mode:
+
+- Build the book then close the prompt with `Ctrl+C`
+
+  ```bash
+  hero docs -d
+  ```
+
+- See the book on the local browser
+
+  ```
+  bash /root/hero/var/docusaurus/develop.sh
+  ```
+
+You can then view the website in your browser at `https://localhost:3100`.
+
+## Publish a Website
+
+- To build and publish a Hero website:
+  - Development
+
+    ```bash
+    hero docs -bpd
+    ```
+
+  - Production
+
+    ```bash
+    hero docs -bp
+    ```
+
+If you want to specify a different SSH key, use `-dk`:
+
+```bash
+hero docs -bpd -dk ~/.ssh/id_ed25519
+```
+
+> Note: The container handles the SSH agent and key management automatically on startup, so in most cases, you won't need to manually specify keys.