Feat event bus subscriptions + trigger system (v0.2.2)

Three trigger primitives replacing the old monolithic scheduler:

- Event triggers: extensions subscribe to bus patterns via manifest,
  async handler invocation through sandbox.CallEntryPoint
- Webhook triggers: inbound HTTP at /api/v1/hooks/:pkg/:slug with
  HMAC-SHA256 verification and synchronous Starlark response
- Scheduled tasks: user-created cron scripts with restricted sandbox
  (no raw HTTP, no DB table creation), runs as creator identity

New tables: triggers, scheduled_tasks, trigger_logs (postgres + sqlite).
New permission: triggers.register. Full admin + user CRUD APIs.
SyncManifestTriggers hooked into seed and install flows.

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

server/events/types.go

@@ -80,6 +80,10 @@ var routeTable = map[string]Direction{
 	"extension.loaded":  DirLocal,   // Client-only
 	"extension.error":   DirLocal,
 
+	// Trigger system (v0.2.2)
+	"trigger.fired":     DirLocal,   // Trigger invocation event (observability)
+	"trigger.error":     DirLocal,   // Trigger execution error
+
 	// Heartbeat
 	"ping":  DirFromClient,
 	"pong":  DirToClient,