Improve cockpit typography for readability across all pages.

Raise base font to 16px, enlarge sidebar, buttons, tables and headings, add Inter font and global typography layer.

cockpit/static/css/vertical-tabs.css

@@ -75,7 +75,7 @@
   border-radius: 8px;
   background: transparent;
   color: #94a3b8;
-  font-size: 0.8rem;
+  font-size: 0.9375rem;
   font-weight: 500;
   text-align: left;
   cursor: pointer;
@@ -158,7 +158,7 @@
 }
 .ei-vtab-sub {
   display: block;
-  font-size: 0.62rem;
+  font-size: 0.75rem;
   color: #64748b;
   margin-top: 0.1rem;
 }
@@ -169,7 +169,7 @@
   gap: 0.15rem;
 }
 .ei-vtab-key {
-  font-size: 0.55rem;
+  font-size: 0.6875rem;
   color: #475569;
   font-family: ui-monospace, monospace;
 }
@@ -203,7 +203,7 @@
 .vt-tab-panel-head p,
 .ei-tab-panel-head p {
   margin: 0.1rem 0 0;
-  font-size: 0.72rem;
+  font-size: 0.8125rem;
   color: #64748b;
 }
 .vt-tab-panel-body,