fix(ci): volume mount 不可 rm -rf，改 find -mindepth 1 -delete

/opt/api-venv 是 Docker volume mount，刪目錄本身會 Device or resource busy
改清空內容保留 mount point

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/cd.yaml

@@ -102,9 +102,11 @@ jobs:
             ln -sf "$(which python3)" /usr/local/bin/python3.11 || true
           fi
 
-          if [ ! -d "$VENV" ] || [ "$(cat $HASH_FILE 2>/dev/null)" != "$CURRENT_HASH" ]; then
+          if [ ! -d "$VENV/bin" ] || [ "$(cat $HASH_FILE 2>/dev/null)" != "$CURRENT_HASH" ]; then
             echo "📦 deps 已變更，重建 venv..."
-            rm -rf "$VENV"
+            # 2026-04-17 ogt: /opt/api-venv 是 volume mount，不能 rm -rf 目錄本身
+            # 改用 find 清空內容，保留 mount point 目錄
+            find "$VENV" -mindepth 1 -delete 2>/dev/null || true
             python3.11 -m venv $VENV
             source $VENV/bin/activate
             pip install -q uv