feat: Add tox configuration for OpenStack standard testing

Add tox.ini following OpenStack project standards to support:
- Multiple Python versions testing (py3, py310-313)
- Style checking with ruff (pep8 environment)
- Code formatting (format environment)
- Coverage reporting (cover environment)
- Debug support (debug environment)
- Virtual environment for arbitrary commands (venv environment)

This allows OpenStack contributors to use familiar tox commands
while maintaining uv for fast local development.

Author: paikend

tox.ini

@@ -0,0 +1,69 @@
+[tox]
+minversion = 4.3.0
+envlist = py3,py{310,311,312,313},pep8
+skipsdist = False
+
+[testenv]
+usedevelop = True
+setenv =
+    VIRTUAL_ENV={envdir}
+    OS_STDOUT_CAPTURE=1
+    OS_STDERR_CAPTURE=1
+    OS_TEST_TIMEOUT=60
+deps =
+    -r{toxinidir}/requirements.txt
+    pytest>=8.4.1
+commands =
+    pytest {posargs}
+
+[testenv:pep8]
+description = Run style checks with ruff
+deps =
+    ruff>=0.12.5
+commands =
+    ruff check src tests
+    ruff format --check src tests
+
+[testenv:format]
+description = Auto-format code with ruff
+deps =
+    ruff>=0.12.5
+commands =
+    ruff check --fix src tests
+    ruff format src tests
+
+[testenv:venv]
+description = Run arbitrary commands in a virtual environment
+commands = {posargs}
+
+[testenv:cover]
+description = Generate test coverage report
+deps =
+    {[testenv]deps}
+    coverage>=7.0
+    pytest-cov>=6.0.0
+commands =
+    pytest --cov=openstack_mcp_server --cov-report=html:cover --cov-report=xml:cover/coverage.xml --cov-report=term {posargs}
+
+[testenv:debug]
+description = Run tests with debugging
+commands =
+    pytest --pdb {posargs}
+
+[testenv:docs]
+description = Build documentation (placeholder for future use)
+allowlist_externals = echo
+commands =
+    echo "Documentation building not yet configured"
+
+[testenv:py310]
+basepython = python3.10
+
+[testenv:py311]
+basepython = python3.11
+
+[testenv:py312]
+basepython = python3.12
+
+[testenv:py313]
+basepython = python3.13