feat(api): add API documentation and ShareX integration

- Add an API documentation page with curl and ShareX examples.
- Implement a dynamic ShareX configuration endpoint (`/api/v1/sharex/warpbox-anonymous.sxcu`) that generates a `.sxcu` file pre-configured with the instance's base URL.
- Update anonymous uploads to return a private management link (`manageUrl`) and a deletion link (`deleteUrl`) in JSON responses.
- Update README with details on Stage 3 Anonymous Integrations.
- Add styling for the new API documentation view and management details.

examples/sharex/warpbox-anonymous.sxcu

@@ -0,0 +1,14 @@
+{
+  "Version": "18.0.0",
+  "Name": "Warpbox Anonymous Upload",
+  "DestinationType": "ImageUploader, TextUploader, FileUploader",
+  "RequestMethod": "POST",
+  "RequestURL": "https://warpbox.dev/api/v1/upload",
+  "Headers": {
+    "Accept": "application/json"
+  },
+  "Body": "MultipartFormData",
+  "FileFormName": "sharex",
+  "URL": "$json:boxUrl$",
+  "DeletionURL": "$json:manageUrl$"
+}