chore: start adding overview page

app/helpers/dashboard/variance_helper.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Dashboard
+  module VarianceHelper
+    def heading_gutter
+      30
+    end
+
+    def footer_gutter
+      50
+    end
+
+    def measure_row_height
+      40
+    end
+
+    def graph_height(number_of_rows)
+      number_of_rows * measure_row_height + heading_gutter + footer_gutter
+    end
+
+    def graph_background_height(number_of_rows:)
+      number_of_rows += 1 if @has_empty_dataset
+      graph_height(number_of_rows) - footer_gutter
+    end
+
+    def measure_row_bar_height
+      20
+    end
+
+    def label_width_percentage
+      30
+    end
+
+    def graph_width_percentage
+      100 - label_width_percentage
+    end
+
+    def zones
+      %w[warning watch growth approval ideal]
+    end
+
+    def zone_width_percentage
+      100.0 / zones.size
+    end
+
+    def availability_indicator_percentage
+      3
+    end
+
+    def partial_data_indicator_size
+      20
+    end
+  end
+end