refactor(scripts): extract shared utilities into common module

- Move load_env_file, parse_timeout_seconds, build_remote_script, and
  build_ssh_command to scripts/common.py
- Update remote_docker_run.py to import from common module
- Improves code organization and reusability

.opencode/opencode.json

@@ -2,8 +2,17 @@
   "$schema": "https://opencode.ai/config.json",
   "permission": {
     "bash": {
+      "python": "deny",
+      "python *": "deny",
       "make": "deny",
-      "make *": "deny"
+      "make *": "deny",
+      "just remote *": "ask"
+    },
+    "read": {
+      ".env": "deny"
+    },
+    "edit": {
+      ".env": "deny"
     }
   }
 }