feat: add config module with load_config function

Add TOML configuration file support with:
- ConfigError exception class for config-related errors
- load_config() function to parse TOML files with proper error handling
- Tests for missing file and invalid TOML syntax scenarios

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/__init__.py

@@ -0,0 +1 @@
+# Tests package

tests/test_config.py

@@ -0,0 +1,29 @@
+"""Tests for config module."""
+
+import tempfile
+
+import pytest
+from pathlib import Path
+
+from zzpyjenkins.config import load_config, ConfigError
+
+
+def test_load_config_file_not_found():
+    """Test load_config raises error when config file doesn't exist."""
+    with pytest.raises(ConfigError) as exc_info:
+        load_config(Path("/nonexistent/path/config.toml"))
+    assert "Config file not found" in str(exc_info.value)
+
+
+def test_load_config_invalid_toml():
+    """Test load_config raises error for invalid TOML syntax."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".toml", delete=False) as f:
+        f.write("invalid toml [[[[")
+        temp_path = Path(f.name)
+
+    try:
+        with pytest.raises(ConfigError) as exc_info:
+            load_config(temp_path)
+        assert "Invalid TOML syntax" in str(exc_info.value)
+    finally:
+        temp_path.unlink()