build: add dockerfiles to example repos

As per internal discussion, we should improve the build process by having a dockerfile in each example project which deploys a node & deploys the local contract/enclave code.

Start by locating all example projects in the repository and reviewing how each currently builds and deploys its node, contract, and enclave code. Add a Dockerfile to every example project that supports deploying the node and local contract/enclave code. Done means each example has a working Docker-based deployment path.

Written by the indexing model from the issue text.