feat(layout): add admin panel layout with sidebar and header

- Add Sidebar component with navigation items (dashboard, bookings, tournaments, pos, clients, memberships, reports, settings)
- Add Header component with SiteSwitcher and user info/logout
- Add SiteSwitcher component for SUPER_ADMIN multi-site selection
- Add admin layout wrapper with AuthProvider
- Add placeholder Dashboard page

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/components/layout/site-switcher.tsx

@@ -0,0 +1,119 @@
+'use client';
+
+import { useState, useEffect, useRef } from 'react';
+import { useSession } from 'next-auth/react';
+import { MapPin, ChevronDown, Check } from 'lucide-react';
+import { cn } from '@/lib/utils';
+
+interface Site {
+  id: string;
+  name: string;
+}
+
+export function SiteSwitcher() {
+  const { data: session } = useSession();
+  const [sites, setSites] = useState<Site[]>([]);
+  const [selectedSiteId, setSelectedSiteId] = useState<string | null>(null);
+  const [isOpen, setIsOpen] = useState(false);
+  const [isLoading, setIsLoading] = useState(true);
+  const dropdownRef = useRef<HTMLDivElement>(null);
+
+  const isSuperAdmin = session?.user?.role === 'SUPER_ADMIN';
+
+  useEffect(() => {
+    async function fetchSites() {
+      try {
+        const response = await fetch('/api/sites');
+        if (response.ok) {
+          const data = await response.json();
+          setSites(data.data || []);
+        }
+      } catch (error) {
+        console.error('Failed to fetch sites:', error);
+      } finally {
+        setIsLoading(false);
+      }
+    }
+
+    fetchSites();
+  }, []);
+
+  useEffect(() => {
+    function handleClickOutside(event: MouseEvent) {
+      if (dropdownRef.current && !dropdownRef.current.contains(event.target as Node)) {
+        setIsOpen(false);
+      }
+    }
+
+    document.addEventListener('mousedown', handleClickOutside);
+    return () => document.removeEventListener('mousedown', handleClickOutside);
+  }, []);
+
+  const selectedSite = sites.find((site) => site.id === selectedSiteId);
+  const displayName = selectedSiteId ? selectedSite?.name : 'Todas las sedes';
+
+  // For non-SUPER_ADMIN users, just show their assigned site
+  if (!isSuperAdmin) {
+    const userSiteName = sites.length > 0 ? sites[0]?.name : 'Cargando...';
+    return (
+      <div className="flex items-center gap-2 text-sm text-primary-700">
+        <MapPin className="h-4 w-4 text-primary-500" />
+        <span>{isLoading ? 'Cargando...' : userSiteName}</span>
+      </div>
+    );
+  }
+
+  // For SUPER_ADMIN, show dropdown to select site
+  return (
+    <div className="relative" ref={dropdownRef}>
+      <button
+        onClick={() => setIsOpen(!isOpen)}
+        className={cn(
+          'flex items-center gap-2 rounded-lg border border-primary-200 bg-white px-3 py-2 text-sm font-medium text-primary-700 transition-colors hover:bg-primary-50',
+          isOpen && 'ring-2 ring-primary-500 ring-offset-1'
+        )}
+      >
+        <MapPin className="h-4 w-4 text-primary-500" />
+        <span>{isLoading ? 'Cargando...' : displayName}</span>
+        <ChevronDown className={cn('h-4 w-4 transition-transform', isOpen && 'rotate-180')} />
+      </button>
+
+      {isOpen && (
+        <div className="absolute left-0 top-full z-50 mt-1 w-56 rounded-lg border border-primary-200 bg-white py-1 shadow-lg">
+          <button
+            onClick={() => {
+              setSelectedSiteId(null);
+              setIsOpen(false);
+            }}
+            className={cn(
+              'flex w-full items-center justify-between px-3 py-2 text-sm text-primary-700 hover:bg-primary-50',
+              !selectedSiteId && 'bg-primary-50 font-medium'
+            )}
+          >
+            <span>Todas las sedes</span>
+            {!selectedSiteId && <Check className="h-4 w-4 text-primary" />}
+          </button>
+          <div className="my-1 border-t border-primary-100" />
+          {sites.map((site) => (
+            <button
+              key={site.id}
+              onClick={() => {
+                setSelectedSiteId(site.id);
+                setIsOpen(false);
+              }}
+              className={cn(
+                'flex w-full items-center justify-between px-3 py-2 text-sm text-primary-700 hover:bg-primary-50',
+                selectedSiteId === site.id && 'bg-primary-50 font-medium'
+              )}
+            >
+              <span>{site.name}</span>
+              {selectedSiteId === site.id && <Check className="h-4 w-4 text-primary" />}
+            </button>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
+
+export default SiteSwitcher;