feat(desktop): push publish tasks via AMQP topic dispatch WebSocket

Introduce a desktop.task.dispatch topic exchange with per-client routing
keys. Tenant-api publishes a task_available frame keyed by target client
ID when a publish job is created; every instance binds its own transient
queue and forwards to the matching WebSocket (/api/desktop/dispatch) it
owns. Desktop-client now prefers this push channel and only falls back
to HTTP /lease polling when the socket is down. Also drop admin-web
monitoring-plugin remnants and scope the publish modal account list to
publish platforms.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/shared/config/config.go

@@ -78,6 +78,9 @@ type RabbitMQConfig struct {
 	GenerationDLQRouteKey        string `mapstructure:"generation_dlq_routing_key"`
 	GenerationEventExchange      string `mapstructure:"generation_event_exchange"`
 	DesktopTaskEventExchange     string `mapstructure:"desktop_task_event_exchange"`
+	DesktopDispatchExchange      string `mapstructure:"desktop_dispatch_exchange"`
+	DesktopDispatchPublishPrefix string `mapstructure:"desktop_dispatch_publish_prefix"`
+	DesktopDispatchMonitorPrefix string `mapstructure:"desktop_dispatch_monitor_prefix"`
 	TemplateAssistExchange       string `mapstructure:"template_assist_exchange"`
 	TemplateAssistRoutingKey     string `mapstructure:"template_assist_routing_key"`
 	TemplateAssistQueue          string `mapstructure:"template_assist_queue"`
@@ -475,6 +478,15 @@ func normalizeRabbitMQConfig(cfg *RabbitMQConfig) {
 	if strings.TrimSpace(cfg.DesktopTaskEventExchange) == "" {
 		cfg.DesktopTaskEventExchange = "desktop.task.event"
 	}
+	if strings.TrimSpace(cfg.DesktopDispatchExchange) == "" {
+		cfg.DesktopDispatchExchange = "desktop.task.dispatch"
+	}
+	if strings.TrimSpace(cfg.DesktopDispatchPublishPrefix) == "" {
+		cfg.DesktopDispatchPublishPrefix = "publish"
+	}
+	if strings.TrimSpace(cfg.DesktopDispatchMonitorPrefix) == "" {
+		cfg.DesktopDispatchMonitorPrefix = "monitor"
+	}
 	if strings.TrimSpace(cfg.TemplateAssistExchange) == "" {
 		cfg.TemplateAssistExchange = "template.assist"
 	}