fix: add a per-widget action menu (#27)

A GridStackItem now carries an overflow menu next to the grip and the
close button: refresh, maximize, duplicate, remove. Maximize and remove
are handled by the item itself; refresh and duplicate are only reported,
since what they mean depends on the widget.

Maximizing only sets a class — the item's gs-* attributes and its
gridstack node are untouched, so restoring is by definition the position
it had.

The menu sits outside the drag-handle selector, like the close button, so
opening it never starts a drag; a Playwright test drags it to prove it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0124BiJikbhbiEsNfJxdWM69

src/main/java/com/example/components/Fa.java

@@ -27,6 +27,10 @@ public enum Fa {
     RESET("fa-solid", "fa-arrow-rotate-left"),
     DRAG("fa-solid", "fa-grip-vertical"),
     CLOSE("fa-solid", "fa-xmark"),
+    MENU("fa-solid", "fa-ellipsis-vertical"),
+    REFRESH("fa-solid", "fa-arrows-rotate"),
+    MAXIMIZE("fa-solid", "fa-expand"),
+    DUPLICATE("fa-solid", "fa-clone"),
     TREND_UP("fa-solid", "fa-arrow-trend-up"),
     TREND_DOWN("fa-solid", "fa-arrow-trend-down");