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>

test-doubao-api.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+"""
+豆包（火山引擎 Ark）API 快速测试
+用法: python3 test-doubao-api.py
+"""
+import json, time, sys
+
+try:
+    import requests
+except ImportError:
+    print("需要安装 requests: pip install requests")
+    sys.exit(1)
+
+API_KEY = "18480c26-ebcd-4263-8a6f-48359b8bd65d"
+BASE_URL = "https://ark.cn-beijing.volces.com/api/v3"
+MODEL = "doubao-seed-2-0-pro-260215"
+
+headers = {
+    "Content-Type": "application/json",
+    "Authorization": f"Bearer {API_KEY}"
+}
+
+print("=" * 50)
+print("  豆包 API 测试")
+print("=" * 50)
+
+# ---- 测试 1: 非流式 ----
+print("\n【测试 1】非流式调用")
+payload = {
+    "model": MODEL,
+    "messages": [{"role": "user", "content": "你好，请用一句话介绍你自己"}],
+    "stream": False
+}
+
+start = time.time()
+try:
+    resp = requests.post(f"{BASE_URL}/chat/completions", headers=headers, json=payload, timeout=30)
+    elapsed = (time.time() - start) * 1000
+    print(f"HTTP 状态码: {resp.status_code}")
+    print(f"耗时: {elapsed:.0f} ms")
+    if resp.status_code == 200:
+        data = resp.json()
+        choices = data.get("choices", [])
+        if choices:
+            print(f"回复: {choices[0]['message']['content']}")
+        usage = data.get("usage", {})
+        print(f"Token: prompt={usage.get('prompt_tokens',0)}, completion={usage.get('completion_tokens',0)}, total={usage.get('total_tokens',0)}")
+        print(f"模型: {data.get('model', '?')}")
+    else:
+        print(f"错误: {resp.text[:500]}")
+except Exception as e:
+    elapsed = (time.time() - start) * 1000
+    print(f"请求失败 ({elapsed:.0f}ms): {e}")
+
+# ---- 测试 2: 流式 ----
+print("\n【测试 2】流式调用 (SSE)")
+payload_stream = {
+    "model": MODEL,
+    "messages": [{"role": "user", "content": "简单说一下健康饮食的三个要点，每个要点一句话"}],
+    "stream": True
+}
+
+start2 = time.time()
+first_token_time = None
+full_content = ""
+
+try:
+    resp2 = requests.post(f"{BASE_URL}/chat/completions", headers=headers, json=payload_stream, stream=True, timeout=30)
+    print(f"HTTP 状态码: {resp2.status_code}")
+    if resp2.status_code == 200:
+        print("流式输出: ", end="", flush=True)
+        for line in resp2.iter_lines(decode_unicode=True):
+            if not line:
+                continue
+            if line.startswith("data: "):
+                json_str = line[6:].strip()
+                if json_str == "[DONE]":
+                    break
+                try:
+                    evt = json.loads(json_str)
+                    delta = evt.get("choices", [{}])[0].get("delta", {}).get("content", "")
+                    if delta:
+                        if first_token_time is None:
+                            first_token_time = time.time()
+                        full_content += delta
+                        print(delta, end="", flush=True)
+                except json.JSONDecodeError:
+                    pass
+
+        total_time = (time.time() - start2) * 1000
+        ttft = (first_token_time - start2) * 1000 if first_token_time else 0
+        print(f"\n---")
+        print(f"首字时间 (TTFT): {ttft:.0f} ms")
+        print(f"总耗时: {total_time:.0f} ms")
+        print(f"回复长度: {len(full_content)} 字符")
+    else:
+        print(f"错误: {resp2.text[:500]}")
+except Exception as e:
+    elapsed2 = (time.time() - start2) * 1000
+    print(f"\n请求失败 ({elapsed2:.0f}ms): {e}")
+
+print("\n" + "=" * 50)
+print("  测试完成")
+print("=" * 50)