docs: organize tool pages by modality under /tools/<modality>/

Move all 157 tool pages into image/video/audio/pdf/data subfolders so URLs read /tools/<modality>/<id> (e.g. /tools/image/crop). Nest the image sub-categories under an Image group in the sidebar so the nav reads by modality. Add public/_redirects (301, clean + .html forms) mapping every old flat /tools/<id> URL to its new path so inbound links keep working. Rewrite all internal /tools links. Verified with a clean docs build (no dead links).

apps/docs/tools/data/json-xml.md

@@ -0,0 +1,56 @@
+---
+description: Convert between JSON and XML, both directions.
+---
+
+# JSON to XML
+
+Convert between JSON and XML formats in both directions. Upload a JSON file to get XML, or upload an XML file to get JSON.
+
+## API Endpoint
+
+`POST /api/v1/tools/data/json-xml`
+
+Accepts multipart form data with a JSON or XML file and a JSON `settings` field.
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| pretty | boolean | No | `true` | Pretty-print output with indentation |
+
+## Example Request
+
+JSON to XML:
+
+```bash
+curl -X POST http://localhost:1349/api/v1/tools/data/json-xml \
+  -H "Authorization: Bearer si_your-api-key" \
+  -F "file=@config.json" \
+  -F 'settings={"pretty": true}'
+```
+
+XML to JSON:
+
+```bash
+curl -X POST http://localhost:1349/api/v1/tools/data/json-xml \
+  -H "Authorization: Bearer si_your-api-key" \
+  -F "file=@config.xml" \
+  -F 'settings={"pretty": true}'
+```
+
+## Example Response
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/config.xml",
+  "originalSize": 850,
+  "processedSize": 1200
+}
+```
+
+## Notes
+
+- Conversion direction is auto-detected from the input file extension: `.json` produces `.xml`, and `.xml` produces `.json`.
+- The `pretty` parameter applies to both directions. When `false`, the output is compact with no indentation.
+- XML attributes and nested structures are preserved during round-trip conversion where possible.