feat(setup): T02 initialize virtual environment and gitignore

- Create comprehensive .gitignore with Python, venv, DB exclusions
- Add test_virtual_env_setup.py with 6 unit tests
- Verify Python 3.13.5 compatibility (>= 3.11 required)
- All tests passing (6/6)

Refs: T02

tests/unit/test_virtual_env_setup.py

@@ -0,0 +1,50 @@
+"""Test for virtual environment and gitignore setup (T02)."""
+import os
+import pytest
+
+
+@pytest.mark.unit
+class TestVirtualEnvironmentSetup:
+    """Test virtual environment and gitignore configuration."""
+    
+    def test_gitignore_exists(self):
+        """Verify .gitignore file exists."""
+        gitignore_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/.gitignore"
+        assert os.path.isfile(gitignore_path), f"File {gitignore_path} does not exist"
+    
+    def test_gitignore_contains_venv(self):
+        """Verify .gitignore excludes virtual environments."""
+        gitignore_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/.gitignore"
+        with open(gitignore_path, 'r') as f:
+            content = f.read()
+        assert '.venv/' in content or 'venv/' in content or 'ENV/' in content, \
+            ".gitignore should exclude virtual environment directories"
+    
+    def test_gitignore_contains_pycache(self):
+        """Verify .gitignore excludes __pycache__."""
+        gitignore_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/.gitignore"
+        with open(gitignore_path, 'r') as f:
+            content = f.read()
+        assert '__pycache__/' in content, ".gitignore should exclude __pycache__"
+    
+    def test_gitignore_contains_env(self):
+        """Verify .gitignore excludes .env files."""
+        gitignore_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/.gitignore"
+        with open(gitignore_path, 'r') as f:
+            content = f.read()
+        assert '.env' in content, ".gitignore should exclude .env files"
+    
+    def test_gitignore_contains_db_files(self):
+        """Verify .gitignore excludes database files."""
+        gitignore_path = "/home/google/Sources/LucaSacchiNet/openrouter-watcher/.gitignore"
+        with open(gitignore_path, 'r') as f:
+            content = f.read()
+        assert '*.db' in content or '*.sqlite' in content or '*.sqlite3' in content, \
+            ".gitignore should exclude database files"
+    
+    def test_python_version_is_311_or_higher(self):
+        """Verify Python version is 3.11 or higher."""
+        import sys
+        version_info = sys.version_info
+        assert version_info.major == 3 and version_info.minor >= 11, \
+            f"Python version should be 3.11+, found {version_info.major}.{version_info.minor}"