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/xml-to-csv.md

@@ -0,0 +1,43 @@
+---
+description: Extract repeating elements from XML into a CSV table.
+---
+
+# XML to CSV
+
+Extract repeating elements from an XML file into a flat CSV table. The tool automatically finds the first array of objects in the XML tree and maps each element to a row.
+
+## API Endpoint
+
+`POST /api/v1/tools/data/xml-to-csv`
+
+Accepts multipart form data with an XML file. No settings field is required.
+
+## Parameters
+
+This tool has no configurable parameters. The repeating element is auto-detected from the XML structure.
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:1349/api/v1/tools/data/xml-to-csv \
+  -H "Authorization: Bearer si_your-api-key" \
+  -F "file=@catalog.xml"
+```
+
+## Example Response
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/catalog.csv",
+  "originalSize": 4500,
+  "processedSize": 1800
+}
+```
+
+## Notes
+
+- Only `.xml` files are accepted as input.
+- The tool scans the XML tree for the first repeating set of sibling elements and uses those as rows.
+- Each unique child element or attribute name becomes a CSV column header.
+- This is a one-way conversion. For bidirectional JSON/XML conversion, use the [JSON to XML](/tools/data/json-xml) tool.