feat: 添加桌面版应用和心跳监控

新增功能：
- src/desktop.py: PyQt6 桌面应用，支持 Droidcam 摄像头
  - 实时视频预览 + 绿色扫描框叠加
  - 空格键快速拍照识别
  - 批量记录管理和 Excel 导出
- heartbeat.py: 服务心跳监控，自动重启 Streamlit
- requirements-desktop.txt: 桌面版专用依赖

Web 版优化：
- src/app.py: 自定义摄像头组件，扫描框叠加到视频流

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app.py

@@ -1,14 +1,30 @@
 import os
 import tempfile
+import base64
 import pandas as pd
 import streamlit as st
+import streamlit.components.v1 as components
 from paddleocr import PaddleOCR
 from processor import extract_info, save_to_excel
 
 os.environ["PADDLE_PDX_DISABLE_MODEL_SOURCE_CHECK"] = "True"
 
-st.set_page_config(page_title="信封信息提取系统", page_icon="📮", layout="wide")
-st.title("📮 信封信息提取系统")
+st.set_page_config(
+    page_title="信封信息提取系统",
+    page_icon="📮",
+    layout="centered",
+    initial_sidebar_state="collapsed",
+)
+
+st.markdown("""
+<style>
+    .stApp { max-width: 100%; }
+    .stButton>button { width: 100%; height: 3em; font-size: 1.2em; }
+    .stDownloadButton>button { width: 100%; height: 3em; }
+</style>
+""", unsafe_allow_html=True)
+
+st.title("📮 信封信息提取")
 
 
 @st.cache_resource
@@ -19,10 +35,10 @@ def load_ocr():
 ocr = load_ocr()
 
 
-def process_image(image_file):
-    """处理单张图片"""
+def process_image(image_data):
+    """处理图片数据"""
     with tempfile.NamedTemporaryFile(delete=False, suffix=".jpg") as tmp:
-        tmp.write(image_file.getvalue())
+        tmp.write(image_data)
         tmp_path = tmp.name
 
     try:
@@ -37,52 +53,195 @@ def process_image(image_file):
         os.unlink(tmp_path)
 
 
-# 文件上传
-uploaded_files = st.file_uploader(
-    "上传信封图片（支持批量）",
-    type=["jpg", "jpeg", "png", "bmp"],
-    accept_multiple_files=True,
-)
+# 自定义摄像头组件，带叠加扫描框
+CAMERA_COMPONENT = """
+<div id="camera-container" style="position:relative; width:100%; max-width:500px; margin:0 auto;">
+    <video id="video" autoplay playsinline style="width:100%; border-radius:10px; background:#000;"></video>
 
-if uploaded_files:
-    all_records = []
+    <!-- 扫描框叠加层 -->
+    <div id="overlay" style="
+        position: absolute;
+        top: 8%;
+        left: 50%;
+        transform: translateX(-50%);
+        width: 88%;
+        height: 70%;
+        border: 3px solid #00ff00;
+        box-sizing: border-box;
+        pointer-events: none;
+    ">
+        <!-- 四角 -->
+        <div style="position:absolute; top:-3px; left:-3px; width:20px; height:20px; border-top:4px solid #00ff00; border-left:4px solid #00ff00;"></div>
+        <div style="position:absolute; top:-3px; right:-3px; width:20px; height:20px; border-top:4px solid #00ff00; border-right:4px solid #00ff00;"></div>
+        <div style="position:absolute; bottom:-3px; left:-3px; width:20px; height:20px; border-bottom:4px solid #00ff00; border-left:4px solid #00ff00;"></div>
+        <div style="position:absolute; bottom:-3px; right:-3px; width:20px; height:20px; border-bottom:4px solid #00ff00; border-right:4px solid #00ff00;"></div>
 
-    progress = st.progress(0)
-    status = st.empty()
+        <!-- 字段提示：邮编(左上)、地址(中间)、联系人+电话(底部) -->
+        <div style="position:absolute; top:8px; left:10px; color:rgba(255,255,255,0.6); font-size:12px;">邮编</div>
+        <div style="position:absolute; top:35%; left:10px; right:10px; color:rgba(255,255,255,0.6); font-size:12px; border-bottom:1px dashed rgba(255,255,255,0.3); padding-bottom:30%;">地址</div>
+        <div style="position:absolute; bottom:8px; left:10px; color:rgba(255,255,255,0.6); font-size:12px;">联系人</div>
+        <div style="position:absolute; bottom:8px; right:10px; color:rgba(255,255,255,0.6); font-size:12px;">电话</div>
+    </div>
 
-    for i, file in enumerate(uploaded_files):
-        status.text(f"正在处理: {file.name}")
-        record, raw_texts = process_image(file)
-        record["文件名"] = file.name
-        all_records.append(record)
-        progress.progress((i + 1) / len(uploaded_files))
+    <!-- 编号提示在框外底部 -->
+    <div style="position:absolute; bottom:18%; left:50%; transform:translateX(-50%); color:rgba(255,255,255,0.6); font-size:11px;">
+        ↑ 编号在此处 ↑
+    </div>
 
-    status.text("处理完成！")
+    <canvas id="canvas" style="display:none;"></canvas>
 
-    # 显示结果表格
-    df = pd.DataFrame(all_records)
-    cols = ["文件名", "编号", "邮编", "地址", "联系人/单位名", "电话"]
-    df = df.reindex(columns=cols)
+    <p id="hint" style="text-align:center; color:#666; margin:10px 0; font-size:14px;">
+        📌 将信封背面对齐绿色框，编号对准底部
+    </p>
 
-    st.subheader("📋 提取结果")
-    st.dataframe(df, use_container_width=True)
+    <button id="capture-btn" onclick="capturePhoto()" style="
+        width: 100%;
+        padding: 15px;
+        font-size: 18px;
+        background: #ff4b4b;
+        color: white;
+        border: none;
+        border-radius: 8px;
+        cursor: pointer;
+        margin-top: 10px;
+    ">📷 拍照识别</button>
+</div>
 
-    # 下载按钮
-    output_path = tempfile.mktemp(suffix=".xlsx")
-    df.to_excel(output_path, index=False)
-    with open(output_path, "rb") as f:
-        st.download_button(
-            label="📥 下载 Excel",
-            data=f,
-            file_name="信封提取结果.xlsx",
-            mime="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
-        )
-    os.unlink(output_path)
+<script>
+const video = document.getElementById('video');
+const canvas = document.getElementById('canvas');
+const hint = document.getElementById('hint');
 
-    # 预览图片和识别详情
-    with st.expander("🔍 查看识别详情"):
-        cols = st.columns(min(3, len(uploaded_files)))
-        for i, file in enumerate(uploaded_files):
-            with cols[i % 3]:
-                st.image(file, caption=file.name, use_container_width=True)
-                st.json(all_records[i])
+// 启动后置摄像头
+async function startCamera() {
+    try {
+        const stream = await navigator.mediaDevices.getUserMedia({
+            video: { facingMode: 'environment', width: { ideal: 1280 }, height: { ideal: 720 } }
+        });
+        video.srcObject = stream;
+    } catch (err) {
+        hint.textContent = '❌ 无法访问摄像头: ' + err.message;
+        console.error(err);
+    }
+}
+
+function capturePhoto() {
+    canvas.width = video.videoWidth;
+    canvas.height = video.videoHeight;
+    canvas.getContext('2d').drawImage(video, 0, 0);
+
+    const dataUrl = canvas.toDataURL('image/jpeg', 0.9);
+
+    // 发送到 Streamlit
+    window.parent.postMessage({
+        type: 'streamlit:setComponentValue',
+        value: dataUrl
+    }, '*');
+
+    hint.textContent = '✅ 已拍照，正在识别...';
+    document.getElementById('capture-btn').disabled = true;
+}
+
+startCamera();
+</script>
+"""
+
+# 初始化 session state
+if "records" not in st.session_state:
+    st.session_state.records = []
+
+# 输入方式选择
+tab_camera, tab_upload = st.tabs(["📷 拍照扫描", "📁 上传图片"])
+
+with tab_camera:
+    # 使用自定义摄像头组件
+    photo_data = components.html(CAMERA_COMPONENT, height=550)
+
+    # 检查是否有拍照数据
+    if "captured_image" not in st.session_state:
+        st.session_state.captured_image = None
+
+    # 文件上传作为备用（用于接收JS传来的数据）
+    uploaded_photo = st.file_uploader(
+        "或直接上传照片",
+        type=["jpg", "jpeg", "png"],
+        key="camera_upload",
+        label_visibility="collapsed"
+    )
+
+    if uploaded_photo:
+        with st.spinner("识别中..."):
+            record, raw_texts = process_image(uploaded_photo.getvalue())
+
+        st.success("✅ 识别完成！")
+
+        col1, col2 = st.columns(2)
+        with col1:
+            st.image(uploaded_photo, caption="拍摄图片", use_container_width=True)
+        with col2:
+            st.metric("邮编", record.get("邮编", "-"))
+            st.metric("电话", record.get("电话", "-"))
+            st.metric("联系人", record.get("联系人/单位名", "-"))
+
+        st.text_area("地址", record.get("地址", ""), disabled=True, height=68)
+        st.text_input("编号", record.get("编号", ""), disabled=True)
+
+        if st.button("✅ 添加到列表", type="primary", key="add_camera"):
+            record["来源"] = "拍照"
+            st.session_state.records.append(record)
+            st.success(f"已添加！当前共 {len(st.session_state.records)} 条记录")
+            st.rerun()
+
+with tab_upload:
+    uploaded_files = st.file_uploader(
+        "选择图片文件",
+        type=["jpg", "jpeg", "png", "bmp"],
+        accept_multiple_files=True,
+        label_visibility="collapsed",
+    )
+
+    if uploaded_files:
+        if st.button("🚀 开始识别", type="primary"):
+            progress = st.progress(0)
+
+            for i, file in enumerate(uploaded_files):
+                with st.spinner(f"处理 {file.name}..."):
+                    record, _ = process_image(file.getvalue())
+                    record["来源"] = file.name
+                    st.session_state.records.append(record)
+                progress.progress((i + 1) / len(uploaded_files))
+
+            st.success(f"完成！已添加 {len(uploaded_files)} 条记录")
+            st.rerun()
+
+# 显示已收集的记录
+st.divider()
+st.subheader(f"📋 已收集 {len(st.session_state.records)} 条记录")
+
+if st.session_state.records:
+    df = pd.DataFrame(st.session_state.records)
+    cols = ["来源", "编号", "邮编", "地址", "联系人/单位名", "电话"]
+    df = df.reindex(columns=[c for c in cols if c in df.columns])
+
+    st.dataframe(df, use_container_width=True, hide_index=True)
+
+    col1, col2 = st.columns(2)
+
+    with col1:
+        output_path = tempfile.mktemp(suffix=".xlsx")
+        df.to_excel(output_path, index=False)
+        with open(output_path, "rb") as f:
+            st.download_button(
+                "📥 下载 Excel",
+                data=f,
+                file_name="信封提取结果.xlsx",
+                mime="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+            )
+        os.unlink(output_path)
+
+    with col2:
+        if st.button("🗑️ 清空列表"):
+            st.session_state.records = []
+            st.rerun()
+else:
+    st.info("👆 使用上方拍照或上传功能添加记录")