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/red-eye-removal.md

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+# Red Eye Removal
+
+AI-powered detection and correction of red eye caused by camera flash.
+
+## API Endpoint
+
+`POST /api/v1/tools/image/red-eye-removal`
+
+**Processing:** Asynchronous (returns 202, poll `/api/v1/jobs/{jobId}/progress` for status via SSE)
+
+**Model bundle:** `face-detection` (200-300 MB)
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| file | file | Yes | - | Image file (multipart) |
+| sensitivity | number | No | `50` | Red eye detection sensitivity (0-100). Higher values detect more subtle red-eye |
+| strength | number | No | `70` | Correction strength (0-100). How aggressively to neutralize red |
+| format | string | No | - | Output format (optional override) |
+| quality | number | No | `90` | Output quality (1-100) |
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:13490/api/v1/tools/image/red-eye-removal \
+  -F "file=@flash-photo.jpg" \
+  -F 'settings={"sensitivity":60,"strength":80}'
+```
+
+## Response
+
+### Initial Response (202 Accepted)
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "async": true
+}
+```
+
+### Progress (SSE at `/api/v1/jobs/{jobId}/progress`)
+
+```
+event: progress
+data: {"phase":"processing","stage":"Detecting red eyes...","percent":40}
+```
+
+### Final Result (via SSE)
+
+```json
+{
+  "phase": "complete",
+  "percent": 100,
+  "result": {
+    "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+    "downloadUrl": "/api/v1/download/{jobId}/flash-photo_redeye_fixed.png",
+    "originalSize": 280000,
+    "processedSize": 290000,
+    "facesDetected": 2,
+    "eyesCorrected": 4
+  }
+}
+```
+
+## Notes
+
+- Requires the `face-detection` model bundle to be installed (200-300 MB).
+- First detects faces, then locates eye regions within each face, and finally identifies and corrects red-eye pixels.
+- The `facesDetected` count indicates how many faces were found; `eyesCorrected` is the total number of individual eyes that had red-eye corrected.
+- Output is always PNG for maximum quality preservation.
+- Supports HEIC/HEIF, RAW, TGA, PSD, EXR, and HDR input formats via automatic decoding.