fix(web): restore pointer cursor on buttons (#595)

Tailwind v4 dropped the v3 preflight rule that set `cursor: pointer` on
`button, [role="button"]`, so every <button> in the web app fell back to
the UA default. <a> elements (nav links, GitHub icon) were unaffected, which
is why only the locale switcher and dark-mode toggle looked broken in the header.

Restore the rule once in globals.css instead of adding `cursor-pointer` to
each of the 18 buttons. `:not(:disabled)` keeps disabled playback controls
on the default cursor.

Closes #594

web/src/app/globals.css

@@ -43,6 +43,13 @@ body {
   -webkit-tap-highlight-color: transparent;
 }
 
+/* Tailwind v4 dropped the preflight rule that gave buttons a pointer cursor,
+   so every <button> fell back to the UA default. */
+button:not(:disabled),
+[role="button"]:not(:disabled) {
+  cursor: pointer;
+}
+
 /* =====================================================
    PROSE-CUSTOM: Premium documentation rendering
    ===================================================== */