style: adjust typography and layout styles in impressum, footer, and navbar

Refined text sizes and spacing across components (`impressum.php`, `footer.php`, `navbar.php`) for improved consistency. Added custom styles for headings and impressum-specific elements in `input.css`.

src/css/input.css

@@ -43,7 +43,7 @@
 
 @layer components {
     p {
-        @apply text-2xl font-serif;
+        @apply text-xl font-serif;
     }
 
     h1 {
@@ -54,8 +54,16 @@
         @apply text-3xl font-sans py-4;
     }
 
+    h3 {
+        @apply text-2xl font-sans font-bold py-2;
+    }
+
     .blockpage p {
         @apply py-4;
     }
 
+    .impressum h2 {
+        @apply text-3xl pt-12;
+    }
+
 }