Add Configuration Management with Ansible project

[tungbq]

Closes #14. (Note: #65 looks like a duplicate of the same ask — leaving that one for you to close/merge as you see fit.)

Summary

Adds projects/ansible-configuration-management/ — a hands-on Ansible best-practices demo: roles, inventory-scoped group vars, a Jinja2 template, and a handler, targeting two ubuntu:22.04 containers via the community.docker connection plugin. No SSH keys, no cloud account, no VMs to provision — just Docker.

• common role — apt baseline packages + a marker file
• webserver role — installs nginx, templates index.html per-host from one shared template, starts nginx, and notifies a reload handler only when the template actually changed
• playbooks/site.yml — bootstraps python3/sudo on the minimal target images via a raw pre-task (a genuinely common real-world gotcha on fresh/minimal hosts), then gathers facts and runs the roles
• demo_project.sh — spins up the two containers, runs the playbook, verifies both hosts serve the expected per-host content, then runs the playbook a second time and expects changed=0 for every host — proving idempotency, not just claiming it
• .github/workflows/verify-ansible-configuration-management.yml — matches the repo's existing per-project verify-*.yml convention
• README.md: row 17 (Configuration Management with Ansible) marked ✔️ Done, now linking to the project folder instead of the issue

Test plan

• Ran the exact committed demo_project.sh end-to-end against real Docker containers on this machine, from a clean slate — first run configured both hosts (changed=6 each), curl confirmed both serve correct per-host content, second run reported changed=0 for both hosts.
• Separately verified the notify/handler path: changed app_environment in inventory/group_vars/all.yml, re-ran — only the template task and the Reload nginx handler showed changed; curl confirmed the served page actually updated to the new value.
• ansible-lint . — 0 failures, 0 warnings, production profile (had to fix one real no-changed-when finding on the reload handler along the way).
• shellcheck demo_project.sh — clean.
• Followed CONTRIBUTING.md's flow and the structure in docs/project_template.md.