Show services discovered by site agents as suggested targets

Stores the sanitised list per site, serves it at /sites/{id}/discovered and adds
it to the target picker. Needs a Reef release containing model.DiscoveredService.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

store.go

@@ -199,9 +199,10 @@ type Server struct {
 	opts Options
 
 	status     map[string]model.MappingStatus
-	mailStatus map[string]string            // mail egress ID -> "" (listening) or an error
-	mailChecks map[string]model.MailCheck   // mail egress ID -> the edge's deliverability report
-	containers map[string][]model.Container // by site ID
+	mailStatus map[string]string                    // mail egress ID -> "" (listening) or an error
+	mailChecks map[string]model.MailCheck           // mail egress ID -> the edge's deliverability report
+	containers map[string][]model.Container         // by site ID
+	discovered map[string][]model.DiscoveredService // by site ID: suggested targets the agent found
 	changed    chan struct{}
 
 	tickets map[string]ticket
@@ -249,6 +250,7 @@ func New(dir string, opts Options) (*Server, error) {
 		mailStatus: map[string]string{},
 		mailChecks: map[string]model.MailCheck{},
 		containers: map[string][]model.Container{},
+		discovered: map[string][]model.DiscoveredService{},
 		changed:    make(chan struct{}),
 		tickets:    map[string]ticket{},
 		oauth:      map[string]oauthState{},