WIP Add wallet transactions route, view

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

app/components/wallet_summary_component.html.erb

@@ -0,0 +1,18 @@
+<section class="w-full grid grid-cols-1 md:grid-cols-12 md:mb-0">
+  <div class="md:col-span-8">
+    <p>
+      Send and receive sats via the Bitcoin Lightning Network.
+    </p>
+  </div>
+  <div class="md:col-span-4 mt-4 md:mt-0">
+    <p class="font-mono md:text-right mb-0 p-4 border border-gray-300 rounded-lg overflow-hidden">
+    <% if @balance %>
+      <span class="text-xl"><%= number_with_delimiter @balance %> sats</span><br>
+      <span class="text-sm text-gray-500">Available balance</span>
+    <% else %>
+      <span class="text-xl">n/a sats</span><br>
+      <span class="text-sm text-gray-500">Balance unavailable</span>
+    <% end %>
+    </p>
+  </div>
+</section>

app/components/wallet_summary_component.rb

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+# frozen_string_literal: true
+
+class WalletSummaryComponent < ViewComponent::Base
+  def initialize(balance:)
+    @balance = balance
+  end
+
+end