feat(core): bind request services and implement registered tasks

Wire plugin services through Bind/InjectFrom and AppContext so HTTP and
workers resolve dependencies after Apply. Register TaskHandler objects
with persisted results, and implement send_email_code, mail:send,
cleanup_inactive_users, and dispatch_bot_msg.

backend/plugins/drivers/driver_inproc_worker/plugin.go

@@ -119,13 +119,7 @@ func (p *Plugin) ConfigEnabled(view core.ConfigView) bool {
 func (p *Plugin) Apply(ctx *core.Context) error {
 	p.coreCtx = ctx
 
-	if db, err := core.Inject[contracts.DBService](ctx); err == nil && db != nil {
-		setDBService(db)
-	} else {
-		core.When[contracts.DBService](ctx, func(db contracts.DBService) {
-			setDBService(db)
-		})
-	}
+	core.Bind[contracts.DBService](ctx, setDBService)
 
 	taskSvc := newInprocTaskService(ctx.Tasks())
 	core.Provide[contracts.TaskService](ctx, taskSvc)
@@ -151,6 +145,9 @@ func (p *Plugin) Start(ctx context.Context) error {
 	if p.queue == nil {
 		p.queue = NewInprocQueue(p.concurrency, p.queueCapacity, p.coreCtx.Tasks())
 	}
+	if p.coreCtx != nil {
+		p.queue.appCtx = p.coreCtx.Root()
+	}
 
 	globalMu.Lock()
 	globalQueue = p.queue