Clean repository and update .gitignore

- Remove build artifacts from git tracking (build/, dist/, __pycache__/, *.spec)
- Updated .gitignore to properly exclude generated files
- Added old_code/ documentation folder
- Updated sample_data.txt to show new 5-field format
- Exclude user-specific conf/app.conf from tracking

LabelPrinter.spec

@@ -1,38 +0,0 @@
-# -*- mode: python ; coding: utf-8 -*-
-
-
-a = Analysis(
-    ['label_printer_gui.py'],
-    pathex=[],
-    binaries=[],
-    datas=[],
-    hiddenimports=['kivy', 'PIL', 'barcode', 'reportlab', 'print_label', 'print_label_pdf'],
-    hookspath=[],
-    hooksconfig={},
-    runtime_hooks=[],
-    excludes=[],
-    noarchive=False,
-    optimize=0,
-)
-pyz = PYZ(a.pure)
-
-exe = EXE(
-    pyz,
-    a.scripts,
-    a.binaries,
-    a.datas,
-    [],
-    name='LabelPrinter',
-    debug=False,
-    bootloader_ignore_signals=False,
-    strip=False,
-    upx=True,
-    upx_exclude=[],
-    runtime_tmpdir=None,
-    console=False,
-    disable_windowed_traceback=False,
-    argv_emulation=False,
-    target_arch=None,
-    codesign_identity=None,
-    entitlements_file=None,
-)