system updater: complete overhaul

Move system update flow to GO, with a CLI (convenient AIO tool) and
server integration. All lifecycle, scheduling, execution occurs on
backend side.

Run some backends via pkexec, some via terminal like paru/yay.

Incorporate flatpak as an option to update.

Add terminal override setting in GUI, in addition to $TERMINAL env
variable.

fixes #2307
fixes #822
fixes #1102
fixes #1812
fixes #1087
fixes #1743

core/internal/server/server.go

@@ -30,6 +30,7 @@ import (
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/loginctl"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/models"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/network"
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/sysupdate"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/thememode"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/trayrecovery"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/wayland"
@@ -75,6 +76,7 @@ var wlContext *wlcontext.SharedContext
 var themeModeManager *thememode.Manager
 var trayRecoveryManager *trayrecovery.Manager
 var locationManager *location.Manager
+var sysUpdateManager *sysupdate.Manager
 var geoClientInstance geolocation.Client
 
 const dbusClientID = "dms-dbus-client"
@@ -421,6 +423,19 @@ func InitializeLocationManager(geoClient geolocation.Client) error {
 	return nil
 }
 
+func InitializeSysUpdateManager() error {
+	manager, err := sysupdate.NewManager()
+	if err != nil {
+		log.Warnf("Failed to initialize sysupdate manager: %v", err)
+		return err
+	}
+
+	sysUpdateManager = manager
+
+	log.Info("Sysupdate manager initialized")
+	return nil
+}
+
 func handleConnection(conn net.Conn) {
 	defer conn.Close()
 
@@ -506,6 +521,10 @@ func getCapabilities() Capabilities {
 		caps = append(caps, "dbus")
 	}
 
+	if sysUpdateManager != nil {
+		caps = append(caps, "sysupdate")
+	}
+
 	return Capabilities{Capabilities: caps}
 }
 
@@ -576,6 +595,10 @@ func getServerInfo() ServerInfo {
 		caps = append(caps, "dbus")
 	}
 
+	if sysUpdateManager != nil {
+		caps = append(caps, "sysupdate")
+	}
+
 	return ServerInfo{
 		APIVersion:   APIVersion,
 		CLIVersion:   CLIVersion,
@@ -1243,6 +1266,38 @@ func handleSubscribe(conn net.Conn, req models.Request) {
 		}()
 	}
 
+	if shouldSubscribe("sysupdate") && sysUpdateManager != nil {
+		wg.Add(1)
+		sysupdateChan := sysUpdateManager.Subscribe(clientID + "-sysupdate")
+		go func() {
+			defer wg.Done()
+			defer sysUpdateManager.Unsubscribe(clientID + "-sysupdate")
+
+			initialState := sysUpdateManager.GetState()
+			select {
+			case eventChan <- ServiceEvent{Service: "sysupdate", Data: initialState}:
+			case <-stopChan:
+				return
+			}
+
+			for {
+				select {
+				case state, ok := <-sysupdateChan:
+					if !ok {
+						return
+					}
+					select {
+					case eventChan <- ServiceEvent{Service: "sysupdate", Data: state}:
+					case <-stopChan:
+						return
+					}
+				case <-stopChan:
+					return
+				}
+			}
+		}()
+	}
+
 	if shouldSubscribe("dbus") && dbusManager != nil {
 		wg.Add(1)
 		dbusChan := dbusManager.SubscribeSignals(dbusClientID)
@@ -1348,6 +1403,9 @@ func cleanupManagers() {
 	if locationManager != nil {
 		locationManager.Close()
 	}
+	if sysUpdateManager != nil {
+		sysUpdateManager.Close()
+	}
 	if geoClientInstance != nil {
 		geoClientInstance.Close()
 	}
@@ -1733,6 +1791,10 @@ func Start(printDocs bool) error {
 		}
 	}()
 
+	if err := InitializeSysUpdateManager(); err != nil {
+		log.Warnf("Sysupdate manager unavailable: %v", err)
+	}
+
 	log.Info("")
 	log.Infof("Ready! Capabilities: %v", getCapabilities().Capabilities)