Fix barcode generation and add comprehensive test results

- Fixed double .png extension issue in barcode generation
- Added test data file for demonstrating functionality
- Updated gitignore to allow test data while excluding output files
- Comprehensive testing of PDF generation pipeline
- All core features working: barcode generation, PDF creation, data processing
- Added detailed test results documentation

Test summary:
✅ Virtual environment setup
✅ Python dependencies installation
✅ UPC-A barcode generation (3-6KB PNG files)
✅ Professional PDF catalog generation (161KB output)
✅ Markdown formatting and file organization
✅ Error handling and fallbacks

test_data.json

@@ -0,0 +1,26 @@
+[
+  {
+    "title": "Pokemon Trading Card Game Battle Academy",
+    "price": "$19.95",
+    "stock": "In Stock",
+    "sku": "DG12345678",
+    "image_url": "https://via.placeholder.com/300x200?text=Pokemon+Battle+Academy",
+    "url": "https://www.dollargeneral.com/p/pokemon-battle-academy"
+  },
+  {
+    "title": "Pokemon TCG Scarlet & Violet Booster Pack",
+    "price": "$4.25",
+    "stock": "In Stock", 
+    "sku": "DG87654321",
+    "image_url": "https://via.placeholder.com/300x200?text=Pokemon+Booster+Pack",
+    "url": "https://www.dollargeneral.com/p/pokemon-scarlet-violet-booster"
+  },
+  {
+    "title": "Pokemon Tin Collection Box",
+    "price": "$12.95",
+    "stock": "Low Stock",
+    "sku": "DG11223344",
+    "image_url": "https://via.placeholder.com/300x200?text=Pokemon+Tin+Box",
+    "url": "https://www.dollargeneral.com/p/pokemon-tin-collection"
+  }
+]