feat: 添加 OCR 词汇提取功能

新增 OCR 页面，用户可上传教材词汇表截图，使用 GLM-4.6V 视觉模型
提取单词-释义对并保存到指定文件夹。

- AI 管道: src/lib/bigmodel/ocr/ (orchestrator, types)
- 后端模块: src/modules/ocr/ (action-service-repository 架构)
- 前端页面: src/app/(features)/ocr/ (拖拽上传、folder 选择)
- i18n: 8 种语言翻译支持

messages/zh-CN.json

@@ -197,6 +197,35 @@
     "favorites": "收藏",
     "settings": "设置"
   },
+  "ocr": {
+    "title": "OCR 词汇提取",
+    "description": "上传教材词汇表截图，提取单词-释义对",
+    "uploadImage": "上传图片",
+    "dragDropHint": "拖放图片到此处，或点击选择",
+    "supportedFormats": "支持格式：JPG、PNG、WebP",
+    "selectFolder": "选择文件夹",
+    "chooseFolder": "选择保存提取词汇的文件夹",
+    "noFolders": "暂无文件夹，请先创建文件夹",
+    "languageHints": "语言提示（可选）",
+    "sourceLanguageHint": "源语言（如：英语）",
+    "targetLanguageHint": "目标/翻译语言（如：中文）",
+    "process": "处理图片",
+    "processing": "处理中...",
+    "preview": "预览",
+    "extractedPairs": "提取的词汇对",
+    "word": "单词",
+    "definition": "释义",
+    "pairsCount": "已提取 {count} 个词汇对",
+    "savePairs": "保存到文件夹",
+    "saving": "保存中...",
+    "saved": "成功将 {count} 个词汇对保存到 {folder}",
+    "saveFailed": "保存失败",
+    "noImage": "请先上传图片",
+    "noFolder": "请选择文件夹",
+    "processingFailed": "OCR 处理失败",
+    "tryAgain": "请尝试上传更清晰的图片",
+    "detectedLanguages": "检测到：{source} → {target}"
+  },
   "profile": {
     "myProfile": "我的个人资料",
     "email": "邮箱：{email}",