chore: bump Go to 1.26 and slim docreader dependencies

- Bump base image in docker/Dockerfile.app from golang:1.24 to golang:1.26
  to match `go 1.26` declared in go.mod (fixes CI build failure on
  `go mod download`).
- Drop unused docreader components and their dependencies:
  - Remove `docreader/ocr/` package (paddle/vlm/dummy backends are
    unreferenced by the main flow; OCR/VLM is handled by the Go App).
  - Remove `docreader/parser/storage.py` (dead code; image persistence
    happens in the Go App via inline ImageRef bytes).
  - Remove `docreader/scripts/download_deps.py` (PaddleOCR pre-download).
  - Drop deps: paddleocr, paddlepaddle, openai, ollama, minio,
    cos-python-sdk-v5, oss2, asyncio, pypdf2, markdown, mistletoe,
    goose3, markdownify, pdfplumber, antiword, urllib3.
- Re-lock uv.lock: 145 -> 79 packages.
- Update docreader/README.md to reflect that OCR/VLM/storage are no
  longer configured at the docreader level.

docreader/scripts/download_deps.py

@@ -1,70 +0,0 @@
-#!/usr/bin/env python
-# -*- coding: utf-8 -*-
-
-import sys
-import os
-import logging
-from paddleocr import PaddleOCR
-
-# 添加当前目录到Python路径
-current_dir = os.path.dirname(os.path.abspath(__file__))
-if current_dir not in sys.path:
-    sys.path.append(current_dir)
-
-# 导入ImageParser
-from parser.image_parser import ImageParser
-
-# 配置日志
-logging.basicConfig(
-    level=logging.INFO,
-    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
-    datefmt="%Y-%m-%d %H:%M:%S",
-)
-logger = logging.getLogger(__name__)
-
-
-def init_ocr_model():
-    """Initialize PaddleOCR model to pre-download and cache models"""
-    try:
-        logger.info("Initializing PaddleOCR model for pre-download...")
-        
-        # 使用与代码中相同的配置
-        ocr_config = {
-            "use_gpu": False,
-            "text_det_limit_type": "max",
-            "text_det_limit_side_len": 960,
-            "use_doc_orientation_classify": True,  # 启用文档方向分类
-            "use_doc_unwarping": False,
-            "use_textline_orientation": True,  # 启用文本行方向检测
-            "text_recognition_model_name": "PP-OCRv4_server_rec",
-            "text_detection_model_name": "PP-OCRv4_server_det",
-            "text_det_thresh": 0.3,
-            "text_det_box_thresh": 0.6,
-            "text_det_unclip_ratio": 1.5,
-            "text_rec_score_thresh": 0.0,
-            "ocr_version": "PP-OCRv4",
-            "lang": "ch",
-            "show_log": False,
-            "use_dilation": True,
-            "det_db_score_mode": "slow",
-        }
-        
-        # 初始化PaddleOCR，这会触发模型下载和缓存
-        ocr = PaddleOCR(**ocr_config)
-        logger.info("PaddleOCR model initialization completed successfully")
-        
-        # 测试OCR功能以确保模型正常工作
-        import numpy as np
-        from PIL import Image
-        
-        # 创建一个简单的测试图像
-        test_image = np.ones((100, 300, 3), dtype=np.uint8) * 255
-        test_pil = Image.fromarray(test_image)
-        
-        # 执行一次OCR测试
-        result = ocr.ocr(np.array(test_pil), cls=False)
-        logger.info("PaddleOCR test completed successfully")
-        
-    except Exception as e:
-        logger.error(f"Failed to initialize PaddleOCR model: {str(e)}")
-        raise