feat(ai-chat): 新增豆包API + AI模型配置项支持动态切换

- 后端新增豆包（火山引擎Ark）API集成：DoubaoController、ToolDoubaoServiceImpl，
  使用OkHttp3 SSE流式对话，兼容OpenAI Chat Completions格式
- 新增DoubaoConfig配置类，读取doubao.api.*配置
- 在eb_system_config表新增ai_chat_model配置项，支持doubao/coze/gemini三种模型切换
- 新增GET /api/front/doubao/ai-model-config接口供前端读取当前模型配置
- 前端ai-nutritionist.vue的sendToAI按系统配置分发到_sendViaDoubao/_sendViaCoze/_sendViaGemini
- 前端models-api.js新增doubaoChatStream/doubaoChat/getAiModelConfig函数
- 附带豆包API测试脚本和数据库初始化SQL

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

msh_single_uniapp/api/models-api.js

@@ -812,6 +812,163 @@ function cozeTextToSpeech(data) {
   })
 }
 
+/**
+ * 获取 AI 对话模型配置
+ * @returns {Promise} { data: { model: "doubao" | "coze" | "gemini" } }
+ */
+function getAiModelConfig() {
+  return request('/api/front/doubao/ai-model-config')
+}
+
+/**
+ * 豆包（火山引擎 Ark）- 非流式对话
+ * @param {object} data 请求参数 { messages: [{role, content}], model?, temperature?, maxTokens? }
+ * @returns {Promise} 对话响应（OpenAI Chat Completions 格式）
+ */
+function doubaoChat(data) {
+  return request('/api/front/doubao/chat', {
+    method: 'POST',
+    data: data
+  })
+}
+
+/**
+ * 豆包（火山引擎 Ark）- 流式对话 (SSE + enableChunked)
+ * 返回 OpenAI 兼容的 SSE 事件流：choices[0].delta.content
+ * @param {object} data 请求参数 { messages: [{role, content}] }
+ * @returns {object} 控制器 { onMessage(deltaText), onError, onComplete, abort }
+ */
+function doubaoChatStream(data) {
+  let _onMessage = () => {}
+  let _onError = () => {}
+  let _onComplete = () => {}
+  let _buffer = ''
+  let _task = null
+  let _gotChunks = false
+
+  const controller = {
+    onMessage(fn) { _onMessage = fn; return controller },
+    onError(fn) { _onError = fn; return controller },
+    onComplete(fn) { _onComplete = fn; return controller },
+    abort() { if (_task) _task.abort() },
+    getTask() { return _task }
+  }
+
+  /** 从 SSE data JSON 中提取增量文本（OpenAI 兼容格式） */
+  const extractDeltaText = (evt) => {
+    if (evt && Array.isArray(evt.choices) && evt.choices[0]) {
+      const delta = evt.choices[0].delta
+      if (delta && typeof delta.content === 'string') return delta.content
+      const msg = evt.choices[0].message
+      if (msg && typeof msg.content === 'string') return msg.content
+    }
+    return ''
+  }
+
+  const parseSseLines = (text) => {
+    _buffer += text
+    const lines = _buffer.split('\n')
+    _buffer = lines.pop() || ''
+    for (const line of lines) {
+      const trimmed = line.trim()
+      if (!trimmed || trimmed.startsWith(':')) continue
+      if (trimmed === 'data: [DONE]') continue
+      if (trimmed.startsWith('data:')) {
+        const jsonStr = trimmed.slice(5).trim()
+        if (!jsonStr) continue
+        try {
+          const evt = JSON.parse(jsonStr)
+          const delta = extractDeltaText(evt)
+          if (delta) _onMessage(delta)
+        } catch (e) {
+          console.warn('[doubaoChatStream] JSON parse failed:', jsonStr.slice(0, 200))
+        }
+      }
+    }
+  }
+
+  const parseSseResponseBody = (body) => {
+    if (!body || typeof body !== 'string') return
+    const lines = body.split('\n')
+    for (const line of lines) {
+      const trimmed = line.trim()
+      if (!trimmed || trimmed.startsWith(':')) continue
+      if (trimmed === 'data: [DONE]') continue
+      if (trimmed.startsWith('data:')) {
+        const jsonStr = trimmed.slice(5).trim()
+        if (!jsonStr) continue
+        try {
+          const evt = JSON.parse(jsonStr)
+          const delta = extractDeltaText(evt)
+          if (delta) _onMessage(delta)
+        } catch (e) {
+          console.warn('[doubaoChatStream] JSON parse failed in body fallback:', jsonStr.slice(0, 200))
+        }
+      }
+    }
+  }
+
+  const token = store.state && store.state.app && store.state.app.token
+  _task = uni.request({
+    url: `${API_BASE_URL}/api/front/doubao/chat/stream`,
+    method: 'POST',
+    data: data,
+    header: {
+      'Content-Type': 'application/json',
+      'Accept': 'text/event-stream',
+      ...(token ? { [TOKENNAME]: token } : {})
+    },
+    enableChunked: true,
+    responseType: 'text',
+    success: (res) => {
+      console.log('[doubaoChatStream] success: statusCode=', res.statusCode, '_gotChunks=', _gotChunks)
+      if (res.statusCode !== 200) {
+        let errMsg = '请求失败: ' + res.statusCode
+        try {
+          const body = typeof res.data === 'string' ? JSON.parse(res.data) : res.data
+          if (body && body.message) errMsg = body.message
+          else if (body && body.error && body.error.message) errMsg = body.error.message
+        } catch (e) { /* keep default message */ }
+        _onError(new Error(errMsg))
+        return
+      }
+      // 处理 buffer 中残余内容
+      if (_buffer.trim()) {
+        parseSseLines('\n')
+      }
+      // 不支持 chunked 的环境降级：从完整 response body 解析
+      if (!_gotChunks && res && res.data) {
+        const body = typeof res.data === 'string' ? res.data : JSON.stringify(res.data)
+        parseSseResponseBody(body)
+      }
+      _onComplete()
+    },
+    fail: (err) => {
+      console.error('[doubaoChatStream] request fail:', err)
+      _onError(err)
+    }
+  })
+
+  if (_task && _task.onChunkReceived) {
+    _task.onChunkReceived((res) => {
+      _gotChunks = true
+      try {
+        const bytes = new Uint8Array(res.data)
+        let text = ''
+        for (let i = 0; i < bytes.length; i++) {
+          text += String.fromCharCode(bytes[i])
+        }
+        text = decodeURIComponent(escape(text))
+        parseSseLines(text)
+      } catch (e) {
+        console.warn('[doubaoChatStream] chunk decode error:', e)
+      }
+    })
+  }
+
+  return controller
+}
+
 export default {
   request,
   getArticleById,
@@ -835,5 +992,10 @@ export default {
   cozeWorkflowStream,
   cozeWorkflowResume,
   cozeUploadFile,
-  cozeTextToSpeech
+  cozeTextToSpeech,
+  // 豆包 API
+  doubaoChat,
+  doubaoChatStream,
+  // AI 模型配置
+  getAiModelConfig
 }