Install Open Babel for MOL2 ligand export

Dockerfile

@@ -74,6 +74,23 @@ RUN set -eux; \
     echo "meeko install failed after retries"; \
     exit 1
 
+# Open Babel provides obabel for MOL2 ligand export
+RUN set -eux; \
+    for i in 1 2 3 4 5; do \
+      if conda install -y -c conda-forge openbabel; then \
+        conda clean -afy; \
+        which obabel; \
+        obabel -V; \
+        exit 0; \
+      fi; \
+      echo "openbabel install failed on attempt ${i}, retrying..."; \
+      conda clean -i -y || true; \
+      sleep $((i * 20)); \
+    done; \
+    echo "openbabel install failed after retries"; \
+    exit 1
+
+
 # -----------------------------
 # DeepPurpose affinity env
 # -----------------------------