feat: tree view for cached objects, top-files stats on dashboard (#48)

- Objects page renders paths as a collapsible tree instead of flat list
  with expand/collapse all, aggregated size/hits per directory
- Dashboard gains top-files-by-hits and top-files-by-bandwidth tables
- Backend: new /api/v2/stats/top-files-by-hits and
  /api/v2/stats/top-files-by-bandwidth endpoints
- Raised per_page max to 5000 for objects listing

---------

Co-authored-by: Ben Vincent <ben@unkin.net>
Reviewed-on: #48

internal/api/v2/stats.go

@@ -20,6 +20,8 @@ func (h *StatsHandler) Routes() chi.Router {
 	r := chi.NewRouter()
 	r.Get("/", h.overview)
 	r.Get("/top-remotes", h.topRemotes)
+	r.Get("/top-files-by-hits", h.topFilesByHits)
+	r.Get("/top-files-by-bandwidth", h.topFilesByBandwidth)
 	return r
 }
 
@@ -40,3 +42,21 @@ func (h *StatsHandler) topRemotes(w http.ResponseWriter, r *http.Request) {
 	}
 	writeJSON(w, http.StatusOK, remotes)
 }
+
+func (h *StatsHandler) topFilesByHits(w http.ResponseWriter, r *http.Request) {
+	files, err := h.db.GetTopFilesByHits(r.Context(), 10)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	writeJSON(w, http.StatusOK, files)
+}
+
+func (h *StatsHandler) topFilesByBandwidth(w http.ResponseWriter, r *http.Request) {
+	files, err := h.db.GetTopFilesByBandwidth(r.Context(), 10)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	writeJSON(w, http.StatusOK, files)
+}