feat: the admin Overview shows who is listening, downloads, the library and its disk, and the server's version, uptime and recent errors; a download waiting on you, a client not answering or a full disk count in its verdict (M504 #5627 #5628 #5629 #5630)

The version moves to internal/buildinfo, so /rest/ping reports the build
instead of "dev".

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

internal/server/server.go

@@ -15,6 +15,7 @@ import (
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/api"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/auth"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/buildinfo"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/coverart"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
@@ -232,8 +233,8 @@ func (s *Server) handleHealthz(w http.ResponseWriter, _ *http.Request) {
 	w.WriteHeader(http.StatusOK)
 	_ = json.NewEncoder(w).Encode(map[string]string{
 		"status":             "ok",
-		"version":            ServerVersion,
-		"channel":            ServerChannel,
+		"version":            buildinfo.Version,
+		"channel":            buildinfo.Channel,
 		"min_client_version": MinClientVersion,
 	})
 }