Add System Health view with status and diagnostics

New Health section in the Manage group combining hermes status and
hermes doctor output:

- Version header with update available banner (e.g. "47 commits behind")
- Summary badges: passing/warning/issue counts
- Status sections: environment, API keys, auth providers, terminal
  backend, messaging platforms, gateway service, scheduled jobs
- Diagnostics sections: Python environment, required/optional packages,
  config files, directory structure, external tools, API connectivity,
  submodules, tool availability, Skills Hub, Honcho memory
- Each check shows green/orange/red icon with label and detail
- Refresh button to re-run both commands

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scarf/scarf/Navigation/AppCoordinator.swift

@@ -11,6 +11,7 @@ enum SidebarSection: String, CaseIterable, Identifiable {
     case tools = "Tools"
     case gateway = "Gateway"
     case cron = "Cron"
+    case health = "Health"
     case logs = "Logs"
     case settings = "Settings"
 
@@ -28,6 +29,7 @@ enum SidebarSection: String, CaseIterable, Identifiable {
         case .tools: return "wrench.and.screwdriver"
         case .gateway: return "antenna.radiowaves.left.and.right"
         case .cron: return "clock.arrow.2.circlepath"
+        case .health: return "stethoscope"
         case .logs: return "doc.text"
         case .settings: return "gearshape"
         }