Refactor setup workflow and make install robust via virtualenv

- Introduce a dedicated Python virtualenv (deps target) and run all setup scripts through it
- Fix missing PyYAML errors in clean, CI, and Nix environments
- Refactor build defaults into cli/setup for clearer semantics
- Make setup deterministic and independent from system Python
- Replace early Makefile shell expansion with runtime evaluation
- Rename messy-test to test-messy and update deploy logic and tests accordingly
- Keep setup and test targets consistent across Makefile, CLI, and unit tests

https://chatgpt.com/share/693de226-00ac-800f-8cbd-06552b2f283c

cli/deploy/dedicated.py

@@ -95,8 +95,8 @@ def run_ansible_playbook(
     # 4) Test Phase
     # ---------------------------------------------------------
     if not skip_tests:
-        print("\n🧪 Running tests (make messy-test)...\n")
-        subprocess.run(["make", "messy-test"], check=True)
+        print("\n🧪 Running tests (make test-messy)...\n")
+        subprocess.run(["make", "test-messy"], check=True)
     else:
         print("\n🧪 Tests skipped (--skip-tests)\n")