WIP Add wallet transactions route, view

Adds a new component for the wallet summary as well, and makes the
component tests work with RSpec.

spec/components/wallet_summary_component_spec.rb

@@ -0,0 +1,11 @@
+require "rails_helper"
+
+RSpec.describe WalletSummaryComponent, type: :component do
+  it "renders the balance as a human-readable number" do
+    expect(
+      render_inline(described_class.new(balance: 2301000)) {}.css("section").to_html
+    ).to include(
+      "2,301,000 sats"
+    )
+  end
+end