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/ocr.md

@@ -0,0 +1,58 @@
+# OCR / Text Extraction
+
+Extract text from images using AI-powered optical character recognition. Supports multiple languages and quality tiers.
+
+## API Endpoint
+
+`POST /api/v1/tools/image/ocr`
+
+**Processing:** Synchronous (returns extracted text directly, though progress is reported via SSE if a `clientJobId` is provided)
+
+**Model bundle:** `ocr` (3-4 GB)
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| file | file | Yes | - | Image file (multipart) |
+| quality | string | No | `"balanced"` | Quality tier: `fast` (Tesseract), `balanced` (PaddleOCR v5), `best` (PaddleOCR VL) |
+| language | string | No | `"auto"` | Language hint: `auto`, `en`, `de`, `fr`, `es`, `zh`, `ja`, `ko` |
+| enhance | boolean | No | `true` | Pre-process image for better OCR accuracy |
+| engine | string | No | - | Deprecated. Use `quality` instead. Maps `tesseract` to `fast`, `paddleocr` to `balanced` |
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:13490/api/v1/tools/image/ocr \
+  -F "file=@document.png" \
+  -F 'settings={"quality":"best","language":"en","enhance":true}'
+```
+
+## Response (200 OK)
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "filename": "document.png",
+  "text": "Extracted text content from the image...",
+  "engine": "paddleocr-vl"
+}
+```
+
+### Progress (SSE, optional)
+
+If a `clientJobId` is provided, progress events are streamed:
+
+```
+event: progress
+data: {"phase":"processing","stage":"Recognizing text...","percent":50}
+```
+
+## Notes
+
+- Requires the `ocr` model bundle to be installed (3-4 GB).
+- Unlike most AI tools, OCR returns a synchronous JSON response with extracted text (not an image download URL).
+- Uses a fallback chain: if a higher-quality tier crashes (e.g., PaddleOCR segfault), it automatically retries with the next lower tier.
+- If a tier returns empty text without crashing, it also falls back to the next tier.
+- Quality tiers map to engines: `fast` = Tesseract, `balanced` = PaddleOCR v5, `best` = PaddleOCR VL.
+- Supports HEIC/HEIF, RAW, TGA, PSD, EXR, and HDR input formats via automatic decoding.