Style anchors with underline + leaf color for visibility

Body-copy mailto links ("Chris @ FCI") and the chrome nav link
were rendering as plain text, hard to spot. Added an @layer base
rule that gives every `a[href]` a 1px underline at 2px offset and
the FCI Seed Grant green, with a subtle hover thicken. Tailwind
utilities still win on a per-element basis (the nav link keeps its
`text-ink-soft` color, the brand-image wrapper opts out via
`no-underline`).

app/globals.css

@@ -112,6 +112,24 @@ input, select, textarea, button {
   border-radius: 4px;
 }
 
+/* Anchor defaults. Body links (in copy and chrome) read as interactive
+ * affordances: FCI leaf color + a 1px underline with a small offset.
+ * Lives in @layer base so Tailwind utility classes (text-*, no-underline)
+ * still win on elements that opt out individually. */
+@layer base {
+  a[href] {
+    color: var(--color-leaf-700);
+    text-decoration: underline;
+    text-decoration-thickness: 1px;
+    text-underline-offset: 2px;
+    transition: color 150ms ease-out, text-decoration-thickness 150ms ease-out;
+  }
+  a[href]:hover {
+    color: var(--color-leaf-800);
+    text-decoration-thickness: 1.5px;
+  }
+}
+
 /* Date input chevron styled to match */
 input[type="date"]::-webkit-calendar-picker-indicator {
   opacity: 0.5;