feat(codex-image): 封装 GPT Image 2 图片接口并收紧错误处理

- 新增 openai:image 路由、planner 与 finalize，内部通过 Codex responses image_generation tool 执行生图

- 补充 Codex OAuth/header 兼容、图片 success report 本地处理与相关前后端/集成测试

- 禁止 chat/completions 使用 gpt-image-2，图片接口限制 n=1，并移除 Provider 模型页的图片能力开关

apps/aether-gateway/src/handlers/admin/request/models.rs

@@ -120,6 +120,7 @@ impl<'a> AdminAppState<'a> {
             payload.supports_function_calling,
             payload.supports_streaming,
             payload.supports_extended_thinking,
+            payload.supports_image_generation,
             payload.is_active,
             config,
         )
@@ -226,6 +227,11 @@ impl<'a> AdminAppState<'a> {
             } else {
                 existing.supports_extended_thinking
             },
+            if fields.contains("supports_image_generation") {
+                payload.supports_image_generation
+            } else {
+                existing.supports_image_generation
+            },
             payload.is_active.unwrap_or(existing.is_active),
             payload.is_available.unwrap_or(existing.is_available),
             config,