feat: 后台管理增加提供商动态管理功能

- 新增：添加新的大模型接口提供商
- 新增：编辑已有提供商的参数（API地址、Key、模型列表等）
- 新增：删除提供商
- 新增：拖拽排序调整auto模式的优先级顺序
- 新增：启用/禁用提供商开关
- 优化：主服务动态读取配置，后台修改实时生效

data/config.json

@@ -0,0 +1,35 @@
+{
+  "providers": [
+    {
+      "id": "local-qwen",
+      "name": "Local Qwen",
+      "priority": 1,
+      "base_url": "http://192.168.2.5:1234/v1",
+      "api_key": "sk-lm-fuP5tGU8:Hi7YU87jHyDP6Ay8Tl2j",
+      "models": ["qwen3.5-4b", "qwen3.5", "qwen"],
+      "default_model": "qwen3.5-4b",
+      "timeout": 120,
+      "enabled": true
+    },
+    {
+      "id": "siliconflow-deepseek",
+      "name": "SiliconFlow DeepSeek",
+      "priority": 2,
+      "base_url": "https://api.siliconflow.cn/v1",
+      "api_key": "sk-fhpoexpptvjghpnphtaxbkhjwulzovoqfffbckcfscjmwhcg",
+      "models": ["Pro/deepseek-ai/DeepSeek-V3.2", "deepseek-v3", "deepseek"],
+      "default_model": "Pro/deepseek-ai/DeepSeek-V3.2",
+      "timeout": 120,
+      "enabled": true
+    }
+  ],
+  "model_aliases": {
+    "auto": "auto",
+    "qwen": "qwen3.5-4b",
+    "qwen3.5": "qwen3.5-4b",
+    "qwen3.5-4b": "qwen3.5-4b",
+    "deepseek": "Pro/deepseek-ai/DeepSeek-V3.2",
+    "deepseek-v3": "Pro/deepseek-ai/DeepSeek-V3.2",
+    "deepseek-v3.2": "Pro/deepseek-ai/DeepSeek-V3.2"
+  }
+}