feat: admin password change with confirmation in team panel

Add "Admin Actions" section (superadmin-only, collapsed by default) with
password + confirm fields, eye toggle, mismatch validation, and success toast.
Delete button moved here too.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/i18n/en.json

@@ -234,6 +234,10 @@
   "team.defaultPassword": "Default: changeme123",
   "team.confirmPassword": "Confirm Password",
   "team.passwordsDoNotMatch": "Passwords do not match",
+  "team.adminActions": "Admin Actions",
+  "team.newPassword": "New password (min 6 characters)",
+  "team.changePassword": "Change Password",
+  "team.passwordChanged": "Password changed successfully",
   "team.optional": "(optional)",
   "team.fixedRole": "Fixed role for managers",
   "team.remove": "Remove",