修正缺省图片模型校验用例的 fixture 模型 key

- 将 editor_generation_pricing_rejects_missing_required_image_size 的 fixture 从已退役的 gpt-image-2 换成 gpt-image-2.5-flare-c / gpt-image-2.5-sunburst-c
- 同步断言文案为 models.gpt-image-2.5-flare-c 缺少 2K 的泥点配置，使缺档校验仍覆盖真实必填模型

server-rs/crates/api-server/src/editor_generation_config.rs

@@ -1108,10 +1108,14 @@ mod tests {
                   "unit": "perGeneration",
                   "prices": { "0.5K": 8, "1K": 12, "2K": 24 }
                 },
-                "gpt-image-2": {
+                "gpt-image-2.5-flare-c": {
                   "unit": "perGeneration",
                   "prices": { "1K": 20 }
                 },
+                "gpt-image-2.5-sunburst-c": {
+                  "unit": "perGeneration",
+                  "prices": { "1K": 3, "2K": 5 }
+                },
                 "seedance2.0-fast": {
                   "unit": "perSecond",
                   "prices": { "480p": 10, "720p": 20, "1080p": 40 }
@@ -1145,6 +1149,10 @@ mod tests {
         )
         .expect_err("missing 2K price should fail");
 
-        assert!(error.to_string().contains("gpt-image-2 缺少 2K"));
+        assert!(
+            error
+                .to_string()
+                .contains("models.gpt-image-2.5-flare-c 缺少 2K 的泥点配置")
+        );
     }
 }