fix: restructure src layout to proper package directory

Move src/__init__.py, detect.py, diagnose.py, extract_temp.py, utils/
into src/infrared_data/ to fix wheel package structure. Previously the
whl placed files at root instead of infrared_data/ directory, causing
ModuleNotFoundError on install.

Also update pyproject.toml packages.find config to use standard
src-layout discovery.

src/infrared_data/__init__.py

@@ -0,0 +1,6 @@
+# Infrared Fault Detection Package
+from .diagnose import FaultDiagnoser
+from .detect import InfraredDetector
+from .extract_temp import TempFeatureExtractor
+
+__all__ = ['FaultDiagnoser', 'InfraredDetector', 'TempFeatureExtractor']