refactor: update shell scripts for AI-Trader-Server rebrand

Update all shell scripts to use the new AI-Trader-Server naming throughout.

Changes:
- main.sh: Update comments and echo statements
- entrypoint.sh: Update startup message
- scripts/validate_docker_build.sh: Update title, container name references,
  and docker image tag from ai-trader-test to ai-trader-server-test
- scripts/test_api_endpoints.sh: Update title and docker-compose command

Part of Phase 4: Internal Configuration & Metadata (Task 19)

scripts/test_api_endpoints.sh

@@ -5,7 +5,7 @@
 set -e
 
 echo "=========================================="
-echo "AI-Trader API Endpoint Testing"
+echo "AI-Trader-Server API Endpoint Testing"
 echo "=========================================="
 echo ""
 
@@ -34,7 +34,7 @@ echo "Checking if API is accessible..."
 if ! curl -f "$API_BASE_URL/health" &> /dev/null; then
     echo -e "${RED}✗${NC} API is not accessible at $API_BASE_URL"
     echo "Make sure the container is running:"
-    echo "  docker-compose up -d ai-trader"
+    echo "  docker-compose up -d ai-trader-server"
     exit 1
 fi
 echo -e "${GREEN}✓${NC} API is accessible"