chore(systemd): remove obsolete systemd service files and update infrastructure documentation

- Remove 8 unused systemd service files from coordinator-api/systemd/
  - aitbc-adaptive-learning.service (port 8005)
  - aitbc-advanced-ai.service
  - aitbc-enterprise-api.service
  - aitbc-gpu-multimodal.service (port 8003)
  - aitbc-marketplace-enhanced.service (port 8006)
  - aitbc-modality-optimization.service (port 8004)
  - aitbc-multimodal.service (port 8002)
  - aitbc-openclaw-enhanced.service (port 8007

scripts/detect-aitbc-user.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# AITBC User Detection Script
+# Returns the appropriate user to run AITBC services
+
+if id "aitbc" >/dev/null 2>&1; then
+    echo "aitbc"
+elif id "oib" >/dev/null 2>&1; then
+    echo "oib"
+else
+    echo "root"
+fi