various fix

backend/app/algo_host/cjk_font.py

@@ -0,0 +1,21 @@
+"""Resolve a CJK-capable font for offline visualization subprocesses."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+# Keep in sync with algorithm_subprocesses/5.15/visualize_result_video.py
+CJK_FONT_CANDIDATES: tuple[Path, ...] = (
+    Path("/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc"),
+    Path("/usr/share/fonts/opentype/noto/NotoSerifCJK-Regular.ttc"),
+    Path("/usr/share/fonts/truetype/noto/NotoSansCJK-Regular.ttc"),
+    Path("/usr/share/fonts/truetype/wqy/wqy-microhei.ttc"),
+    Path("/usr/share/fonts/truetype/wqy/wqy-zenhei.ttc"),
+)
+
+
+def resolve_cjk_font_path() -> Path | None:
+    for candidate in CJK_FONT_CANDIDATES:
+        if candidate.is_file():
+            return candidate.resolve()
+    return None