Optimize Docker build: add .dockerignore to skip large models

.dockerignore

@@ -0,0 +1,17 @@
+# Exclude large AI models from Docker context (they download at runtime)
+image_authenticity/.cache/
+.cache/
+
+# Exclude local Next.js frontend
+frontend/
+
+# Exclude git and environment local files
+.git/
+.env
+.env.local
+node_modules/
+__pycache__/
+
+# Exclude large documentation files
+*.docx
+*.pdf