feat: tree view for cached objects, top-files stats on dashboard

- 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

internal/api/v2/objects.go

@@ -28,7 +28,7 @@ func (h *ObjectsHandler) Routes() chi.Router {
 func (h *ObjectsHandler) list(w http.ResponseWriter, r *http.Request) {
 	remoteName := chi.URLParam(r, "name")
 	limit, _ := strconv.Atoi(r.URL.Query().Get("per_page"))
-	if limit <= 0 || limit > 100 {
+	if limit <= 0 || limit > 5000 {
 		limit = 50
 	}
 	page, _ := strconv.Atoi(r.URL.Query().Get("page"))

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)
+}

internal/database/stats.go

@@ -76,3 +76,68 @@ func (db *DB) GetTopRemotes(ctx context.Context, limit int) ([]RemoteStatRow, er
 	}
 	return result, rows.Err()
 }
+
+type FileStatRow struct {
+	RemoteName  string `json:"remote_name"`
+	Path        string `json:"path"`
+	AccessCount int64  `json:"access_count"`
+	SizeBytes   int64  `json:"size_bytes"`
+}
+
+func (db *DB) GetTopFilesByHits(ctx context.Context, limit int) ([]FileStatRow, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT a.remote_name, a.path, a.access_count, b.size_bytes
+		FROM artifacts a
+		JOIN blobs b ON a.content_hash = b.content_hash
+		ORDER BY a.access_count DESC
+		LIMIT $1
+	`, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []FileStatRow
+	for rows.Next() {
+		var r FileStatRow
+		if err := rows.Scan(&r.RemoteName, &r.Path, &r.AccessCount, &r.SizeBytes); err != nil {
+			return nil, err
+		}
+		result = append(result, r)
+	}
+	return result, rows.Err()
+}
+
+type BandwidthStatRow struct {
+	RemoteName string `json:"remote_name"`
+	Path       string `json:"path"`
+	Bandwidth  int64  `json:"bandwidth"`
+	Requests   int64  `json:"requests"`
+}
+
+func (db *DB) GetTopFilesByBandwidth(ctx context.Context, limit int) ([]BandwidthStatRow, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT remote_name, path,
+			COALESCE(SUM(size_bytes), 0) AS bandwidth,
+			COUNT(*) AS requests
+		FROM access_log
+		WHERE created_at > NOW() - INTERVAL '30 days'
+		GROUP BY remote_name, path
+		ORDER BY bandwidth DESC
+		LIMIT $1
+	`, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []BandwidthStatRow
+	for rows.Next() {
+		var r BandwidthStatRow
+		if err := rows.Scan(&r.RemoteName, &r.Path, &r.Bandwidth, &r.Requests); err != nil {
+			return nil, err
+		}
+		result = append(result, r)
+	}
+	return result, rows.Err()
+}