feat: add downloadable release management for desktop client

- Extend DesktopClientReleaseCheckResponse with platform, arch, and channel fields.
- Introduce DesktopClientDownloadableRelease and DesktopClientDownloadableReleaseListResponse interfaces for managing downloadable releases.
- Implement ListDownloadable method in DesktopClientReleaseService to retrieve downloadable releases based on the specified channel.
- Update DesktopClientReleaseCheckResult to include platform, arch, and channel information.
- Add resolveInstallerDownloadURL method to handle download URL resolution for releases.
- Create new endpoint in DesktopReleaseHandler for listing downloadable releases.
- Update router to include the new downloadable releases route.
- Enhance tests to cover the new functionality for resolving download URLs and listing downloadable releases.

server/internal/tenant/transport/desktop_release_handler.go

@@ -85,6 +85,15 @@ func (h *DesktopReleaseHandler) DownloadURLPublic(c *gin.Context) {
 	response.Success(c, data)
 }
 
+func (h *DesktopReleaseHandler) ListDownloadable(c *gin.Context) {
+	data, err := h.svc.ListDownloadable(c.Request.Context(), c.DefaultQuery("channel", "stable"))
+	if err != nil {
+		response.Error(c, err)
+		return
+	}
+	response.Success(c, data)
+}
+
 func (h *DesktopReleaseHandler) UpdaterFeedPublic(c *gin.Context) {
 	feed, err := h.svc.ResolveLatestUpdaterFeed(c.Request.Context(), opsapp.DesktopClientReleaseCheckInput{
 		Platform:       firstNonEmpty(c.Param("platform"), c.Query("platform")),

server/internal/tenant/transport/router.go

@@ -98,6 +98,9 @@ func RegisterRoutes(app *bootstrap.App) {
 	media := tenantProtected.Group("/media")
 	media.GET("/platforms", mediaHandler.ListPlatforms)
 
+	desktopClient := tenantProtected.Group("/desktop-client")
+	desktopClient.GET("/releases/downloadable", desktopReleaseHandler.ListDownloadable)
+
 	mediaSupplyHandler := NewMediaSupplyHandler(app)
 	mediaSupply := tenantProtected.Group("/media-supply")
 	mediaSupply.GET("/resources", mediaSupplyHandler.ListResources)