优化AI图像显示，添加发送图片到UCD

app/services/ai_image.py

@@ -122,10 +122,40 @@ def list_records(base_dir: Optional[str] = None) -> List[AIImageRecord]:
                 extra=extra,
             )
         )
+    if not records:
+        seeded = _seed_placeholder_record(cache_dir)
+        if seeded is not None:
+            records.append(seeded)
     records.sort(key=lambda r: r.created_at, reverse=True)
     return records
 
 
+def _seed_placeholder_record(cache_dir: str) -> Optional[AIImageRecord]:
+    """当缓存为空时，写入一张本地占位图，便于前端联调。"""
+    try:
+        repo_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+        src = os.path.join(repo_root, "assets", "entry_1.png")
+        if not os.path.isfile(src):
+            return None
+
+        rec_id = f"{_dt.datetime.now().strftime('%Y%m%d_%H%M%S')}_placeholder"
+        image_path = os.path.join(cache_dir, f"{rec_id}.png")
+        shutil.copyfile(src, image_path)
+
+        record = AIImageRecord(
+            id=rec_id,
+            prompt="本地测试占位图（后端未接入）",
+            image_path=image_path,
+            created_at=_dt.datetime.now().isoformat(timespec="seconds"),
+            extra={"source": "local-placeholder"},
+        )
+        with open(_meta_path_for(image_path), "w", encoding="utf-8") as f:
+            f.write(record.to_json())
+        return record
+    except Exception:
+        return None
+
+
 def save_image_to_cache(
     prompt: str,
     image_bytes: bytes,