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/handlers/extensions.go

@@ -12,6 +12,7 @@ import (
 	"switchboard-core/database"
 	"switchboard-core/models"
 	"switchboard-core/store"
+	"switchboard-core/triggers"
 )
 
 // ExtensionHandler serves extension management endpoints.
@@ -239,6 +240,9 @@ func (h *ExtensionHandler) AdminInstallExtension(c *gin.Context) {
 		}
 	}
 
+	// v0.2.2: Sync triggers from manifest
+	SyncManifestTriggers(c.Request.Context(), h.stores, triggers.GlobalEngine(), pkg.ID, manifestMap)
+
 	c.JSON(201, gin.H{"data": pkg})
 }