Add comprehensive test suite for QuantUI

Introduce a full pytest-based test suite for QuantUI. Adds tests/ with conftest.py (shared fixtures for sample molecules, temp dirs, and pytest markers) and many test modules covering core functionality: ase_bridge (ASE integration, round-trips, file reading, presets), calculator (PySCFCalculation setup, script generation, descriptions/notes, factory), comparison (CalcSummary builders, HTML table, plotting), help_content (help topics and widget), molecule (validation, parsing, properties, presets), plus additional test modules for notebook interactions, optimizer, orbital visualization, phase1, preopt, progress, pubchem, security, session_calc, templates, utils, and visualization_integration. ASE-dependent tests are skipped gracefully when ASE is not available. This commit adds extensive unit and integration tests to improve coverage and catch regressions.

Author: NCCU-Schultz-Lab

tests/__init__.py

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+"""
+QuantUI Test Suite
+
+Tests for all QuantUI modules.
+"""

tests/conftest.py

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+"""
+Pytest Configuration and Fixtures
+
+Shared test fixtures for QuantUI test suite.
+"""
+
+import pytest
+from pathlib import Path
+
+
+@pytest.fixture
+def sample_water_xyz():
+    """Simple water molecule XYZ coordinates."""
+    return """O  0.0  0.0  0.0
+H  0.757  0.587  0.0
+H  -0.757  0.587  0.0"""
+
+
+@pytest.fixture
+def sample_methane_xyz():
+    """Simple methane molecule XYZ coordinates."""
+    return """C  0.0  0.0  0.0
+H  0.63  0.63  0.63
+H  -0.63  -0.63  0.63
+H  -0.63  0.63  -0.63
+H  0.63  -0.63  -0.63"""
+
+
+@pytest.fixture
+def sample_sdf_water():
+    """Sample SDF content for water molecule."""
+    return """
+  Mrv2311 02131511003D
+
+  3  2  0  0  0  0            999 V2000
+    0.0000    0.0000    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
+    0.7570    0.5870    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0
+   -0.7570    0.5870    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0
+  1  2  1  0  0  0  0
+  1  3  1  0  0  0  0
+M  END
+$$$$
+"""
+
+
+@pytest.fixture
+def temp_test_dir(tmp_path):
+    """Create a temporary directory for test files."""
+    test_dir = tmp_path / "quantui_test"
+    test_dir.mkdir()
+    return test_dir
+
+
+# Markers for test categorization
+def pytest_configure(config):
+    """Configure pytest with custom markers."""
+    config.addinivalue_line(
+        "markers", "network: tests that require network connectivity"
+    )
+    config.addinivalue_line(
+        "markers", "slow: tests that take significant time to run"
+    )
+    config.addinivalue_line(
+        "markers", "integration: integration tests requiring external services"
+    )