Initial commit: EbayListingTool WPF application

C# WPF desktop app for creating eBay UK listings with AI-powered
photo analysis. Features: multi-photo vision analysis via OpenRouter
(Claude), local listing save/export, saved listings browser,
single item listing form, bulk import from CSV/Excel, and eBay
OAuth authentication.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,16 @@
+# Build outputs
+bin/
+obj/
+*.user
+*.suo
+.vs/
+
+# Config with secrets — never commit
+EbayListingTool/appsettings.json
+
+# Rider / JetBrains
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db