fix: dashboard updates when switching sites

- Added SiteContext for global site selection state
- Updated admin layout with SiteProvider
- Updated SiteSwitcher to use shared context
- Dashboard now refetches data when site changes

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

apps/web/contexts/site-context.tsx

@@ -0,0 +1,66 @@
+"use client";
+
+import { createContext, useContext, useState, useEffect, ReactNode } from "react";
+
+interface Site {
+  id: string;
+  name: string;
+}
+
+interface SiteContextType {
+  sites: Site[];
+  selectedSiteId: string | null;
+  selectedSite: Site | null;
+  setSelectedSiteId: (siteId: string | null) => void;
+  isLoading: boolean;
+}
+
+const SiteContext = createContext<SiteContextType | undefined>(undefined);
+
+export function SiteProvider({ children }: { children: ReactNode }) {
+  const [sites, setSites] = useState<Site[]>([]);
+  const [selectedSiteId, setSelectedSiteId] = useState<string | null>(null);
+  const [isLoading, setIsLoading] = useState(true);
+
+  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();
+  }, []);
+
+  const selectedSite = sites.find((site) => site.id === selectedSiteId) || null;
+
+  return (
+    <SiteContext.Provider
+      value={{
+        sites,
+        selectedSiteId,
+        selectedSite,
+        setSelectedSiteId,
+        isLoading,
+      }}
+    >
+      {children}
+    </SiteContext.Provider>
+  );
+}
+
+export function useSite() {
+  const context = useContext(SiteContext);
+  if (context === undefined) {
+    throw new Error("useSite must be used within a SiteProvider");
+  }
+  return context;
+}