fix(docker): install libssl-dev to build the openssl gem

The build stage was missing the OpenSSL headers, so bundle install
failed compiling the openssl gem's native extension.

🤖 Assisted by Claude

Dockerfile

@@ -26,7 +26,7 @@ FROM base AS build
 
 # Install packages need to build gems
 RUN apt-get update -qq && \
-    apt-get install -y build-essential git pkg-config libyaml-dev  && \
+    apt-get install -y build-essential git pkg-config libyaml-dev libssl-dev && \
     rm -rf /var/lib/apt/lists /var/cache/apt/archives
 
 # Install application gems