Fix spacing inconsistencies on home screen

- Remove mb-1 from Recent Transactions header (wallet headers have
  no bottom margin, so this should match)
- Remove mb-3 wrapper from wallet sections (section header bg
  provides the visual break, extra margin created uneven gaps)
- Change tx row padding from py-2 to py-1 to match address rows

src/popup/index.html

@@ -220,7 +220,7 @@
                 <!-- recent transactions across all addresses -->
                 <div>
                     <div
-                        class="font-bold bg-section py-1 px-2 mb-1"
+                        class="font-bold bg-section py-1 px-2"
                         style="margin-left: -0.5rem; margin-right: -0.5rem"
                     >
                         Recent Transactions