feat(midsummer): retire the theme out of season (holiday over)

Flip the seasonal master switch (SEASON_ACTIVE=false in useMidsummer) so the
Sma Grodorna theme is fully dormant — no rain/frogs/maypole/banner/palette,
regardless of any stored toggle preference — and remove the 🐸 toggle from the
sidebar. All theme code is kept; to bring it back next Midsummer, flip
SEASON_ACTIVE to true and re-add <FrogToggle /> in SidebarWindowButtons.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/sidebar/SidebarWindowButtons.tsx

@@ -2,7 +2,6 @@ import React, { useCallback } from 'react';
 import { useWindowManager } from '../../contexts/WindowManagerContext';
 import { useCurrentUser } from '../../hooks/useCurrentUser';
 import { logout } from '../../api/endpoints';
-import { FrogToggle } from '../midsummer/FrogToggle';
 
 export const SidebarWindowButtons: React.FC = () => {
   const { openWindow } = useWindowManager();
@@ -16,7 +15,6 @@ export const SidebarWindowButtons: React.FC = () => {
 
   return (
     <div className="ml-tool-links">
-      <FrogToggle />
       <span className="ml-tool-link" style={{ cursor: 'pointer' }}
         onClick={() => openWindow('agent', 'Overlord Assistant')}>🤖 Assistant</span>
       <span className="ml-tool-link" style={{ cursor: 'pointer' }}