feat(setup): T05 configure pytest with coverage

- Create pytest.ini with:
  - Test discovery configuration (testpaths, python_files)
  - Asyncio mode settings
  - Coverage configuration (>=90% requirement)
  - Custom markers (unit, integration, e2e, slow)
- Update conftest.py with:
  - pytest_asyncio plugin
  - Shared fixtures (project_root, src_path, temp_dir, mock_env_vars)
  - Path configuration for imports
- Add test_pytest_config.py with 12 unit tests
- All tests passing (12/12)

Refs: T05

Completes setup phase T01-T05

tests/unit/test_pytest_config.py

@@ -0,0 +1,103 @@
+"""Test for pytest configuration (T05)."""
+import os
+import sys
+import pytest
+
+
+@pytest.mark.unit
+class TestPytestConfiguration:
+    """Test pytest configuration and setup."""
+    
+    def test_pytest_ini_exists(self):
+        """Verify pytest.ini file exists."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        assert os.path.isfile(ini_path), f"File {ini_path} does not exist"
+    
+    def test_pytest_ini_has_testpaths(self):
+        """Verify pytest.ini contains testpaths configuration."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        assert 'testpaths' in content, "pytest.ini should contain testpaths"
+    
+    def test_pytest_ini_has_python_files(self):
+        """Verify pytest.ini contains python_files configuration."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        assert 'python_files' in content, "pytest.ini should contain python_files"
+    
+    def test_pytest_ini_has_python_functions(self):
+        """Verify pytest.ini contains python_functions configuration."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        assert 'python_functions' in content, "pytest.ini should contain python_functions"
+    
+    def test_pytest_ini_has_addopts(self):
+        """Verify pytest.ini contains addopts configuration."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        assert 'addopts' in content, "pytest.ini should contain addopts"
+    
+    def test_pytest_ini_has_cov_config(self):
+        """Verify pytest.ini contains coverage configuration."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        assert 'cov' in content.lower(), "pytest.ini should contain coverage config"
+    
+    def test_conftest_py_exists(self):
+        """Verify conftest.py file exists."""
+        conf_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/tests/conftest.py"
+        assert os.path.isfile(conf_path), f"File {conf_path} does not exist"
+    
+    def test_conftest_py_has_pytest_plugins(self):
+        """Verify conftest.py contains pytest_plugins."""
+        conf_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/tests/conftest.py"
+        with open(conf_path, 'r') as f:
+            content = f.read()
+        assert 'pytest_plugins' in content or 'fixture' in content, \
+            "conftest.py should contain pytest plugins or fixtures"
+    
+    def test_conftest_py_imports_pytest_asyncio(self):
+        """Verify conftest.py imports pytest_asyncio."""
+        conf_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/tests/conftest.py"
+        with open(conf_path, 'r') as f:
+            content = f.read()
+        assert 'pytest_asyncio' in content or 'asyncio' in content.lower(), \
+            "conftest.py should import pytest_asyncio"
+    
+    def test_pytest_can_run_tests(self):
+        """Verify pytest can actually run tests."""
+        import subprocess
+        result = subprocess.run(
+            ['python3', '-m', 'pytest', '--version'],
+            capture_output=True,
+            text=True
+        )
+        assert result.returncode == 0, "pytest should be runnable"
+        assert 'pytest' in result.stdout.lower(), "pytest version should be displayed"
+    
+    def test_pytest_can_discover_tests(self):
+        """Verify pytest can discover tests in the project."""
+        import subprocess
+        result = subprocess.run(
+            ['python3', '-m', 'pytest', '--collect-only', '-q'],
+            capture_output=True,
+            text=True,
+            cwd='/home/google/Sources/LucaSacchiNet/openrouter-watcher'
+        )
+        assert result.returncode == 0, "pytest should collect tests without errors"
+        # Should find at least some tests
+        assert 'test' in result.stdout.lower(), "pytest should find tests"
+    
+    def test_coverage_is_configured(self):
+        """Verify coverage is configured in pytest."""
+        ini_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/pytest.ini"
+        with open(ini_path, 'r') as f:
+            content = f.read()
+        # Check for coverage report configuration
+        assert any(term in content.lower() for term in ['cov-report', 'coverage', 'cov=']), \
+            "pytest.ini should configure coverage reporting"