feat(reports): add MetricFilter concern for hiding metrics

Add Reports::MetricFilter concern that provides methods to filter
hidden metrics from API responses:
- filter_hidden_metrics_from_hash: filters hash responses
- filter_hidden_metrics_from_array: filters array responses
- filter_summary_with_previous: filters summary with nested previous data
- metric_hidden?: checks if a specific metric should be hidden

Includes alias support (avg_reply_time -> reply_time).

app/controllers/concerns/reports/metric_filter.rb

@@ -0,0 +1,59 @@
+module Reports::MetricFilter
+  extend ActiveSupport::Concern
+
+  HIDEABLE_METRICS = %w[outgoing_messages_count incoming_messages_count reply_time].freeze
+
+  # Alias mapping (canonical form)
+  METRIC_ALIASES = {
+    'avg_reply_time' => 'reply_time'
+  }.freeze
+
+  private
+
+  def filter_hidden_metrics_from_hash(data)
+    return data if hidden_metrics.blank?
+
+    data.reject { |key, _| metric_key_hidden?(key) }
+  end
+
+  def filter_hidden_metrics_from_array(data)
+    return data if hidden_metrics.blank?
+
+    data.map { |item| item.reject { |key, _| metric_key_hidden?(key) } }
+  end
+
+  # Filter summary data including nested 'previous' key (handles both symbol and string keys)
+  def filter_summary_with_previous(data)
+    return data if hidden_metrics.blank?
+
+    filtered = filter_hidden_metrics_from_hash(data)
+    previous_data = filtered[:previous] || filtered['previous']
+    if previous_data.present?
+      filtered_previous = filter_hidden_metrics_from_hash(previous_data)
+      # Preserve the original key type
+      if filtered.key?(:previous)
+        filtered[:previous] = filtered_previous
+      else
+        filtered['previous'] = filtered_previous
+      end
+    end
+    filtered
+  end
+
+  def hidden_metrics
+    @hidden_metrics ||= (Current.account.report_hidden_metrics || []) & HIDEABLE_METRICS
+  end
+
+  def metric_hidden?(metric_name)
+    # Normalize to canonical form (e.g., avg_reply_time -> reply_time)
+    normalized = METRIC_ALIASES[metric_name.to_s] || metric_name.to_s
+    hidden_metrics.include?(normalized)
+  end
+
+  # Check if a hash key should be hidden (handles both symbol and string keys, plus aliases)
+  def metric_key_hidden?(key)
+    key_str = key.to_s
+    normalized = METRIC_ALIASES[key_str] || key_str
+    hidden_metrics.include?(normalized)
+  end
+end