Security: dual token + customer guide page

- Split auth into agent-token (public) and controller-token (secret)
- Agent token in scripts can't be used to control devices
- Add agent.html: step-by-step guide for customers (Win/Mac/Linux)
- Update agent binaries with new token defaults

website/agent.sh

@@ -7,7 +7,7 @@
 set -e
 
 RELAY_SERVER="ws://47.107.130.152:8900"
-TOKEN="remote-agent-secret"
+TOKEN="uclaw-agent-pub"
 TIMEOUT_HOURS=2
 AGENT_DIR="/tmp/uclaw"
 AGENT_PATH="$AGENT_DIR/agent"