Consistent headings on home: lighter title rules, thick section dividers

Wallet and Recent Transactions headings now use border-border-light
for their bottom rule. Thick 2px black horizontal rules separate
wallet sections from each other and from the transactions section,
with generous vertical spacing.

src/popup/index.html

@@ -218,8 +218,19 @@
                 <div id="wallet-list"></div>
 
                 <!-- recent transactions across all addresses -->
-                <div class="border-t border-border mt-3 pt-2">
-                    <h3 class="font-bold text-xs mb-1">Recent Transactions</h3>
+                <hr
+                    style="
+                        border: none;
+                        border-top: 2px solid currentColor;
+                        margin: 1rem 0;
+                    "
+                />
+                <div>
+                    <div
+                        class="font-bold border-b border-border-light pb-1 mb-1"
+                    >
+                        Recent Transactions
+                    </div>
                     <div id="home-tx-list">
                         <div class="text-muted text-xs py-1">Loading...</div>
                     </div>