feat(paddleocr): add PaddleOCR OCR service (Docker images, server, tests, docs) and CI workflows

readme.hints.md

@@ -77,6 +77,81 @@ HEALTHCHECK --interval=30s --timeout=10s --start-period=60s --retries=3 \
 
 CPU variant has longer `start-period` (120s) due to slower startup.
 
+## PaddleOCR
+
+### Overview
+
+PaddleOCR is a standalone OCR service using PaddlePaddle's PP-OCRv4 model. It provides:
+
+- Text detection and recognition
+- Multi-language support
+- FastAPI REST API
+- GPU and CPU variants
+
+### Docker Images
+
+| Tag | Description |
+|-----|-------------|
+| `paddleocr` | GPU variant (default) |
+| `paddleocr-gpu` | GPU variant (alias) |
+| `paddleocr-cpu` | CPU-only variant |
+
+### API Endpoints
+
+| Endpoint | Method | Description |
+|----------|--------|-------------|
+| `/health` | GET | Health check with model info |
+| `/ocr` | POST | OCR with base64 image (JSON body) |
+| `/ocr/upload` | POST | OCR with file upload (multipart form) |
+
+### Request/Response Format
+
+**POST /ocr (JSON)**
+```json
+{
+  "image": "<base64-encoded-image>",
+  "language": "en"  // optional
+}
+```
+
+**POST /ocr/upload (multipart)**
+- `img`: image file
+- `language`: optional language code
+
+**Response**
+```json
+{
+  "success": true,
+  "results": [
+    {
+      "text": "Invoice #12345",
+      "confidence": 0.98,
+      "box": [[x1,y1], [x2,y2], [x3,y3], [x4,y4]]
+    }
+  ]
+}
+```
+
+### Environment Variables
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `OCR_LANGUAGE` | `en` | Default language for OCR |
+| `SERVER_PORT` | `5000` | Server port |
+| `SERVER_HOST` | `0.0.0.0` | Server host |
+| `CUDA_VISIBLE_DEVICES` | (auto) | Set to `-1` for CPU-only |
+
+### Performance
+
+- **GPU**: ~1-3 seconds per page
+- **CPU**: ~10-30 seconds per page
+
+### Supported Languages
+
+Common language codes: `en` (English), `ch` (Chinese), `de` (German), `fr` (French), `es` (Spanish), `ja` (Japanese), `ko` (Korean)
+
+---
+
 ## Adding New Models
 
 To add a new model variant: