CSV Transaction Imports (#708)

Introduces a basic CSV import module for bulk-importing account transactions.

Changes include:

- User can load a CSV
- User can configure the column mappings for a CSV
- Imported CSV shows invalid cells
- User can clean up their data directly in the UI
- User can see a preview of the import rows and confirm import
- Layout refactor + Import nav stepper
- System test stability improvements

test/application_system_test_case.rb

@@ -1,21 +1,27 @@
 require "test_helper"
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
-  driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ]
+  driven_by :selenium, using: ENV["CI"].present? ? :headless_chrome : :chrome, screen_size: [ 1400, 1400 ]
 
   private
 
-  def sign_in(user)
-    visit new_session_path
-    within "form" do
-      fill_in "Email", with: user.email
-      fill_in "Password", with: "password"
-      click_button "Log in"
-    end
-  end
+    def sign_in(user)
+      visit new_session_path
+      within "form" do
+        fill_in "Email", with: user.email
+        fill_in "Password", with: "password"
+        click_on "Log in"
+      end
 
-  def sign_out
-    find("#user-menu").click
-    click_button "Logout"
-  end
+      # Trigger Capybara's wait mechanism to avoid timing issues with logins
+      find("h1", text: "Dashboard")
+    end
+
+    def sign_out
+      find("#user-menu").click
+      click_button "Logout"
+
+      # Trigger Capybara's wait mechanism to avoid timing issues with logout
+      find("h2", text: "Sign in to your account")
+    end
 end