fix(bluebubbles): add missing integration points and documentation (#6460)

- hermes_cli/skills_config.py: add platform label for per-platform skill config
- gateway/session.py: add to PII-safe platforms (no mention system)
- website/docs/user-guide/messaging/bluebubbles.md: full setup guide
- website/sidebars.ts: sidebar navigation entry
- 10 docs pages: add BlueBubbles to all platform enumerations
  (env vars, toolsets, cron delivery, gateway internals, etc.)

hermes_cli/skills_config.py

@@ -23,6 +23,7 @@ PLATFORMS = {
     "slack":    "💼 Slack",
     "whatsapp": "📱 WhatsApp",
     "signal":   "📡 Signal",
+    "bluebubbles": "💬 BlueBubbles",
     "email":    "📧 Email",
     "homeassistant": "🏠 Home Assistant",
     "mattermost": "💬 Mattermost",