Add user editing functionality to admin panel with improved UI and self-protection safeguards

Implemented comprehensive user editing in admin dashboard with PATCH endpoint for updating email, display name, role, password, and disabled status. Added validation to prevent admins from demoting or disabling themselves, and duplicate email detection. Refactored AdminPanel to modal-based editor with separate create/edit modes, form state management, and save/cancel actions. Enhanced UI with field labels, checkbox for account status, action

frontend/src/styles/styles.js

@@ -180,6 +180,13 @@ export const styles = {
     fontWeight: 1000,
     color: stylesTokens.textGold,
   },
+  adminFieldLabel: {
+    display: "grid",
+    gap: 5,
+    color: stylesTokens.textDim,
+    fontSize: 12,
+    fontWeight: 800,
+  },
   userRow: {
     display: "grid",
     gridTemplateColumns: "1fr 80px 90px",