Chore: Add Docker containerization support

- Add Dockerfile with multi-stage build for .NET 8
- Include ImageMagick dependencies for Magick.NET
- Add docker-compose.yml with volume mount for receipts
- Add .dockerignore to exclude build artifacts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.yml

@@ -0,0 +1,15 @@
+services:
+  moneymap:
+    build:
+      context: ./MoneyMap
+      dockerfile: Dockerfile
+    container_name: moneymap
+    ports:
+      - "5010:5010"
+    environment:
+      - ConnectionStrings__MoneyMapDb=Server=barge.lan;Database=MoneyMap;User Id=moneymap;Password=YOUR_PASSWORD;TrustServerCertificate=True;
+      - Receipts__StoragePath=/app/receipts
+      - OPENAI_API_KEY=${OPENAI_API_KEY}
+    volumes:
+      - /mnt/docker-data/moneymap/receipts:/app/receipts
+    restart: unless-stopped