feat(ai_image): base_url 设置项支持自定义 OpenAI 兼容网关 v1.1.0

generateOpenAI 支持配置 base_url 指向 OpenAI 兼容网关（如本机
llmsproxy），为空保持官方直连。已实测经 llmsproxy→siliconflow
(Kwai-Kolors/Kolors) 生图出有效 PNG。

example/ai_image/plg.json

@@ -2,14 +2,19 @@
   "name": "ai_image",
   "name_zh": "AI绘图",
   "name_en": "AI Image",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "AI 图像生成插件，支持 OpenAI DALL·E / Stable Diffusion",
   "author": "HomeAgent",
   "entry": "plugin.so",
-  "tags": ["ai", "image", "draw", "generate"],
+  "tags": [
+    "ai",
+    "image",
+    "draw",
+    "generate"
+  ],
   "targets": "linux/amd64",
   "outdir": "dist",
   "bundle": true,
   "replaces": {},
   "source_dirs": []
-}
+}