Refs: offline install via vendored wheels and test verification workflow (see README/playbook updates)

Dockerfile

@@ -1,7 +1,7 @@
-
 # Dockerfile
-# Base build environment for hdwalletpy: Python 3.11 + build tools + venv support
-FROM python:3.11-slim
+# Build environment for hdwalletpy: Python 3.12 + build tools + venv support
+# Used for: (1) Building Linux x86_64 wheels, (2) Development container
+FROM python:3.12-slim
 
 # Install build tools, headers, and venv module
 RUN apt-get update && apt-get install -y --no-install-recommends \
@@ -9,8 +9,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     python3-dev \
     libffi-dev \
     python3-venv \
- && rm -rf /var/lib/apt/lists/*
+    && rm -rf /var/lib/apt/lists/*
 
 # Set working directory for bind mounts
 WORKDIR /app
 
+# Default command (can be overridden)
+CMD ["/bin/bash"]