Initial commit: InvenTree Stock Tool v2

A comprehensive barcode scanning application for InvenTree inventory management.

Features:
- Multi-mode operation (Add/Update/Check/Locate stock)
- Smart duplicate prevention when adding stock
- Barcode scanning with automatic part code cleaning
- Real-time server connection monitoring
- Part information display with images
- Debug mode for troubleshooting

Fixes applied:
- Fixed encoding issues with non-ASCII characters in barcodes
- Fixed API response handling for list and dict formats
- Implemented duplicate prevention using PATCH to update existing stock
- Added comprehensive error handling and logging

Includes test suite for verification of all fixes.

example_config.yaml

@@ -0,0 +1,9 @@
+# InvenTree Stock Tool Configuration
+# Copy this file to ~/.config/scan_and_import.yaml and fill in your details
+
+# Your InvenTree server URL (without trailing slash)
+host: https://inventree.example.com
+
+# Your InvenTree API token
+# Get this from: Settings > User Settings > API Tokens in InvenTree
+token: your-api-token-here