Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/components/shared/HoverActionMenu.tsx

@@ -0,0 +1,60 @@
+import React from 'react';
+import { ActionIcon, Tooltip } from '@mantine/core';
+import styles from '@app/components/shared/HoverActionMenu.module.css';
+
+export interface HoverAction {
+  id: string;
+  icon: React.ReactNode;
+  label: string;
+  onClick: (e: React.MouseEvent) => void;
+  disabled?: boolean;
+  color?: string;
+  hidden?: boolean;
+}
+
+interface HoverActionMenuProps {
+  show: boolean;
+  actions: HoverAction[];
+  position?: 'inside' | 'outside';
+  className?: string;
+}
+
+const HoverActionMenu: React.FC<HoverActionMenuProps> = ({
+  show,
+  actions,
+  position = 'inside',
+  className = ''
+}) => {
+  const visibleActions = actions.filter(action => !action.hidden);
+
+  if (visibleActions.length === 0) {
+    return null;
+  }
+
+  return (
+    <div
+      className={`${styles.hoverMenu} ${position === 'outside' ? styles.outside : styles.inside} ${className}`}
+      style={{ opacity: show ? 1 : 0 }}
+      onMouseDown={(e) => e.stopPropagation()}
+      onMouseUp={(e) => e.stopPropagation()}
+      onClick={(e) => e.stopPropagation()}
+    >
+      {visibleActions.map((action) => (
+        <Tooltip key={action.id} label={action.label}>
+          <ActionIcon
+            size="md"
+            variant="subtle"
+            style={{ color: action.color || 'var(--mantine-color-dimmed)' }}
+            disabled={action.disabled}
+            onClick={action.onClick}
+            c={action.color}
+          >
+            {action.icon}
+          </ActionIcon>
+        </Tooltip>
+      ))}
+    </div>
+  );
+};
+
+export default HoverActionMenu;