Tighten header layout for app-like back button

static/styles.css

@@ -21,9 +21,17 @@ img {
   padding: 0.75rem 1rem;
 }
 
+.header-bar {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  min-height: 1.2rem;
+}
+
 .header h1 {
   margin: 0;
   font-size: 1.2rem;
+  line-height: 1.2;
 }
 
 .header a {
@@ -31,6 +39,19 @@ img {
   text-decoration: none;
 }
 
+.header-back {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 1.5rem;
+  height: 1.5rem;
+  margin: -0.15rem 0;
+  font-size: 1.2rem;
+  line-height: 1;
+  font-weight: bold;
+  flex: 0 0 1.5rem;
+}
+
 .container {
   padding: 1rem;
   max-width: 42rem;