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/image/gif-webp.md

@@ -0,0 +1,48 @@
+---
+description: Convert animated GIF to WebP and vice versa, preserving all frames.
+---
+
+# GIF/WebP Converter
+
+Convert animated GIF files to WebP and vice versa, preserving all frames and animation timing. WebP animations are typically 25-35% smaller than equivalent GIFs.
+
+## API Endpoint
+
+`POST /api/v1/tools/image/gif-webp`
+
+Accepts multipart form data with a GIF or WebP file and a JSON `settings` field.
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| quality | integer | No | `80` | Output quality for WebP encoding (1-100) |
+| lossless | boolean | No | `false` | Use lossless WebP compression |
+| resizePercent | integer | No | `100` | Scale the output by percentage (10-100) |
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:1349/api/v1/tools/image/gif-webp \
+  -H "Authorization: Bearer si_your-api-key" \
+  -F "file=@animation.gif" \
+  -F 'settings={"quality": 85, "resizePercent": 50}'
+```
+
+## Example Response
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/animation.webp",
+  "originalSize": 3500000,
+  "processedSize": 2200000
+}
+```
+
+## Notes
+
+- Only `.gif` and `.webp` files are accepted. Other image formats are not supported by this tool.
+- The conversion direction is automatic: GIF input produces WebP output, and WebP input produces GIF output.
+- The `quality` and `lossless` options only apply when encoding to WebP. When converting to GIF, the output uses the standard GIF palette.
+- Use `resizePercent` to reduce the dimensions (and file size) of large animations.