fix(VBtn): render border in forced-colors mode (#21848)

Co-authored-by: J-Sek <[email protected]>

Author: 06b

packages/vuetify/src/components/VBtn/VBtn.sass

@@ -258,3 +258,15 @@
 
     .v-pagination__item--is-active .v-btn__overlay
       opacity: $button-pagination-active-overlay-opacity
+
+@media (forced-colors: active)
+  .v-btn
+    &:not(
+      &--variant-text,
+      &--variant-plain
+    )
+      border: thin solid
+
+    &:focus-visible
+      outline: 2px solid
+      outline-offset: 2px