feat: Add emoji & icon picker for Help Center categories (#14702)

db/migrate/20260610000000_add_icon_color_to_categories.rb

@@ -0,0 +1,5 @@
+class AddIconColorToCategories < ActiveRecord::Migration[7.1]
+  def change
+    add_column :categories, :icon_color, :string, default: ''
+  end
+end

db/schema.rb

@@ -428,6 +428,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_06_11_184600) do
     t.bigint "parent_category_id"
     t.bigint "associated_category_id"
     t.string "icon", default: ""
+    t.string "icon_color", default: ""
     t.index ["associated_category_id"], name: "index_categories_on_associated_category_id"
     t.index ["locale", "account_id"], name: "index_categories_on_locale_and_account_id"
     t.index ["locale"], name: "index_categories_on_locale"