R-492: delete the always-empty cfg.Paths.HDDPath (field, env binding, every fallback)

Readers (report builder, health check, /api/system, web primaryHDDPath, metrics collector,
AutoDiscoverStoragePaths' fallback parameter) now use the storage registry only. An old
controller.yaml still carrying paths.hdd_path keeps loading (non-strict YAML), pinned by
TestR492_OldConfigWithHDDPathStillLoads.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/api/router.go

@@ -1171,9 +1171,9 @@ func (r *Router) triggerSync(w http.ResponseWriter, _ *http.Request) {
 }
 
 func (r *Router) systemInfo(w http.ResponseWriter, _ *http.Request) {
-	// R-490 / R-465: the same default-storage-path fallback every other reader of the always-empty
-	// cfg.Paths.HDDPath has; without it hdd_configured was false on every box.
-	hddPath := r.cfg.Paths.HDDPath
+	// R-490 / R-465 / R-492: the default storage path is the only source (the always-empty global
+	// paths.hdd_path was deleted in R-492); without it hdd_configured was false on every box.
+	hddPath := ""
 	if r.sett != nil {
 		if p := r.sett.GetDefaultStoragePath(); p != "" {
 			hddPath = p