feat: add multi-architecture Docker build setup

- Add Docker BuildKit builder setup for AMD64 and ARM64 platforms
- Update backend and frontend Dockerfiles with platform flags
- Create comprehensive build scripts for multi-arch workflows
- Add verification script to test multi-architecture images
- Update Makefile with multi-arch Docker targets
- Add detailed documentation for multi-architecture setup

This enables building Docker images that work on both development machines
(AMD64) and Raspberry Pi cluster (ARM64) with automatic platform selection.

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

Makefile

@@ -1,7 +1,7 @@
 # Adopt-a-Street Makefile
 # Provides convenient commands for building and running the application
 
-.PHONY: help install build run dev test clean lint format
+.PHONY: help install build run dev test clean lint format docker-multiarch docker-multiarch-verify
 
 # Default target
 help:
@@ -136,6 +136,22 @@ docker-run:
 	docker run -d -p 5000:5000 --name backend adopt-a-street-backend
 	@echo "Docker containers running!"
 
+# Multi-Architecture Docker
+docker-multiarch-setup:
+	@echo "Setting up multi-architecture Docker builder..."
+	./scripts/setup-multiarch-builder.sh
+
+docker-multiarch-build:
+	@echo "Building and pushing multi-architecture Docker images..."
+	./scripts/build-multiarch.sh
+
+docker-multiarch-verify:
+	@echo "Verifying multi-architecture Docker images..."
+	./scripts/verify-multiarch.sh
+
+docker-multiarch: docker-multiarch-setup docker-multiarch-build docker-multiarch-verify
+	@echo "Multi-architecture Docker workflow complete!"
+
 # Database (for development)
 db-setup:
 	@echo "Setting up MongoDB..."
@@ -164,4 +180,12 @@ quick-start: install env-setup db-setup
 	@echo "2. Run 'make dev' to start development servers"
 	@echo "3. Visit http://localhost:3000 to see the application"
 	@echo ""
-	@echo "For more commands, run 'make help'"
+	@echo "For more commands, run 'make help'"
+	@echo ""
+	@echo "Docker Commands:"
+	@echo "  docker-build              Build single-architecture Docker images"
+	@echo "  docker-run                Run Docker containers"
+	@echo "  docker-multiarch-setup    Setup multi-architecture builder"
+	@echo "  docker-multiarch-build    Build and push multi-arch images"
+	@echo "  docker-multiarch-verify   Verify multi-arch images"
+	@echo "  docker-multiarch          Complete multi-arch workflow"