Agent version tracking — workers tab shows current vs latest version

- Add version column to registered_agents table
- Agents send version on registration (Linux 3.1, Windows 3.0, macOS 3.0)
- workers_list API returns latest_versions per platform
- Workers tab: VERSION column with green check (up-to-date) or red (outdated)
- Outdated agents highlight row and show blue UPDATE button
- Up-to-date agents show dimmed UPDATE button
- Update button dispatches update command immediately

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public_html/agent/jarvis-agent.py

@@ -136,6 +136,7 @@ def register(cfg: dict, state: dict) -> str:
         f"{cfg['jarvis_url']}/api/agent/register",
         {
             "hostname": hostname,
+            "version": AGENT_VERSION,
             "agent_type": agent_type,
             "ip_address": ip,
             "capabilities": capabilities,