feat: 实现多 OCR 提供商架构和完整设置页面

## 主要变更

### OCR 架构
- 新增多提供商 OCR 系统 (Tesseract.js, Baidu OCR, RapidOCR)
- 添加 Provider 基类接口和工厂模式
- 支持 provider 自动选择和降级处理
- 新增 RapidOCR Python HTTP 服务 (端口 8080)

### 路径修复
- 修复 Windows 平台路径解析问题
- 统一路径处理工具 (lib/path.ts)
- 修复 uploads 目录定位问题

### 设置页面重构
- 三个标签页：API 配置、OCR 配置、AI 配置
- API 服务器地址配置
- OCR 服务商配置（Tesseract.js, RapidOCR, 百度 OCR）
- AI 服务商配置（智谱 GLM, MiniMax, DeepSeek, Kimi, OpenAI, Anthropic）

### 端口配置
- 前端端口: 13056
- 后端端口: 13057

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/scripts/rapidocr_server.py

@@ -0,0 +1,114 @@
+"""
+RapidOCR HTTP Server
+为 Node.js 后端提供 OCR API 服务
+"""
+
+from rapidocr_onnxruntime import RapidOCR
+from http.server import HTTPServer, BaseHTTPRequestHandler
+import json
+import base64
+import numpy as np
+from io import BytesIO
+from PIL import Image
+import cv2
+
+# 初始化 RapidOCR
+ocr = RapidOCR()
+
+class OCRHandler(BaseHTTPRequestHandler):
+    def _set_cors(self):
+        """设置 CORS"""
+        self.send_header('Access-Control-Allow-Origin', '*')
+        self.send_header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS')
+        self.send_header('Access-Control-Allow-Headers', 'Content-Type')
+
+    def _send_json(self, data, status=200):
+        """发送 JSON 响应"""
+        self.send_response(status)
+        self.send_header('Content-Type', 'application/json')
+        self._set_cors()
+        self.end_headers()
+        self.wfile.write(json.dumps(data, ensure_ascii=False).encode('utf-8'))
+
+    def do_OPTIONS(self):
+        """处理 OPTIONS 请求"""
+        self.send_response(200)
+        self._set_cors()
+        self.end_headers()
+
+    def do_GET(self):
+        """健康检查"""
+        if self.path == '/health':
+            self._send_json({"status": "ok", "service": "rapidocr"})
+        else:
+            self._send_json({"error": "Not found"}, 404)
+
+    def do_POST(self):
+        """处理 OCR 请求"""
+        if self.path == '/ocr':
+            try:
+                content_length = int(self.headers['Content-Length'])
+                post_data = self.rfile.read(content_length)
+                data = json.loads(post_data.decode('utf-8'))
+
+                # 获取图片数据
+                images = data.get('images', [])
+                if not images:
+                    self._send_json({"error": "No images provided"}, 400)
+                    return
+
+                # 处理第一张图片
+                image_base64 = images[0]
+                image_data = base64.b64decode(image_base64)
+
+                # 转换为 OpenCV 格式
+                nparr = np.frombuffer(image_data, np.uint8)
+                img = cv2.imdecode(nparr, cv2.IMREAD_COLOR)
+
+                if img is None:
+                    self._send_json({"error": "Failed to decode image"}, 400)
+                    return
+
+                # 执行 OCR
+                result, _ = ocr(img)
+
+                # 格式化结果
+                ocr_results = []
+                for line in result:
+                    ocr_results.append({
+                        "text": line[0],
+                        "score": float(line[1]),
+                        "box": line[2]
+                    })
+
+                # 计算平均置信度
+                avg_confidence = 0
+                if ocr_results:
+                    avg_confidence = sum(r["score"] for r in ocr_results) / len(ocr_results)
+
+                self._send_json({
+                    "code": 200,
+                    "msg": "success",
+                    "data": ocr_results
+                })
+
+            except Exception as e:
+                self._send_json({"error": str(e)}, 500)
+        else:
+            self._send_json({"error": "Not found"}, 404)
+
+    def log_message(self, format, *args):
+        """减少日志输出"""
+        pass
+
+def run_server(port=8080):
+    """启动服务器"""
+    server_address = ('', port)
+    httpd = HTTPServer(server_address, OCRHandler)
+    print(f"RapidOCR Server running on port {port}")
+    print(f"Health check: http://localhost:{port}/health")
+    print(f"OCR endpoint: http://localhost:{port}/ocr")
+    httpd.serve_forever()
+
+if __name__ == '__main__':
+    run_server()