feat(dashscope): 添加 mediaBaseUrl 和万相新模型系列

[124608760]

Summary

• Add mediaBaseUrl: "https://dashscope.aliyuncs.com/api/v1" to dashscope provider, enabling media-proxy to correctly route image/video generation requests to DashScope's native API (separate from the OpenAI-compatible chat endpoint)
• Replace outdated wanx-v2 with 5 latest Wan image generation models: wan2.7-image-pro, wan2.7-image, wan2.6-t2i, wan2.2-t2i-plus, wan2.2-t2i-flash
• Update wanx-video → wan2.6-t2v with endpoint metadata
• Fix image size format from x separator to * (DashScope API standard)
• Add endpoint, asyncHeader, taskQueryEndpoint metadata in each model's extra field for skill consumption

摘要

• 为 dashscope provider 添加 mediaBaseUrl，使 media-proxy 能正确路由文生图/视频请求到百炼原生 API
• 用 5 个最新万相模型替换过时的 wanx-v2：wan2.7-image-pro、wan2.7-image、wan2.6-t2i、wan2.2-t2i-plus、wan2.2-t2i-flash
• wanx-video 更新为 wan2.6-t2v，补充端点元数据
• 修正尺寸分隔符为 *（阿里云 API 标准格式）
• 各模型 extra 中添加 endpoint/asyncHeader/taskQueryEndpoint 元数据供技能引用

Test plan

• Run npm test in config-center to validate JSON schema
• Run npm run sync-config-center in main repo to verify sync works
• Verify media-proxy correctly resolves dashscope provider with mediaBaseUrl