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/video/crop-video.md

@@ -0,0 +1,48 @@
+---
+description: Crop a region out of a video.
+---
+
+# Crop Video
+
+Crop a rectangular region out of a video by specifying the region's size and position.
+
+## API Endpoint
+
+`POST /api/v1/tools/video/crop-video`
+
+Accepts multipart form data with a video file and a JSON `settings` field.
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| width | integer | Yes | - | Crop region width in pixels (minimum 16) |
+| height | integer | Yes | - | Crop region height in pixels (minimum 16) |
+| x | integer | No | `0` | Horizontal offset from the top-left corner |
+| y | integer | No | `0` | Vertical offset from the top-left corner |
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:1349/api/v1/tools/video/crop-video \
+  -H "Authorization: Bearer si_your-api-key" \
+  -F "file=@clip.mp4" \
+  -F 'settings={"width": 640, "height": 480, "x": 100, "y": 50}'
+```
+
+## Example Response
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/clip.mp4",
+  "originalSize": 12500000,
+  "processedSize": 5200000
+}
+```
+
+## Notes
+
+- The crop region must fit within the video dimensions. If `x + width` or `y + height` exceeds the source size, the request returns a 400 error.
+- Minimum crop size is 16x16 pixels.
+- Dimensions are rounded to even numbers as required by most video codecs.