Add maintenance mode endpoint for Vercel deployments

Create `api/admin/platform/maintenance.ts` to handle maintenance mode logic as a Vercel serverless function, including GET and POST requests for enabling/disabling and admin verification via Supabase.

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api/admin/platform/maintenance.ts

@@ -0,0 +1,106 @@
+import type { VercelRequest, VercelResponse } from "@vercel/node";
+import { createClient } from "@supabase/supabase-js";
+
+const supabaseUrl = process.env.VITE_SUPABASE_URL || "";
+const supabaseServiceRole = process.env.SUPABASE_SERVICE_ROLE || "";
+
+let maintenanceModeCache: boolean | null = null;
+
+const ADMIN_ROLES = ["admin", "super_admin", "staff", "owner"];
+
+async function verifyAdmin(token: string): Promise<boolean> {
+  if (!supabaseUrl || !supabaseServiceRole) return false;
+  
+  const supabase = createClient(supabaseUrl, supabaseServiceRole);
+  
+  try {
+    const { data: { user }, error } = await supabase.auth.getUser(token);
+    if (error || !user) return false;
+    
+    const { data: roles } = await supabase
+      .from("user_roles")
+      .select("role")
+      .eq("user_id", user.id);
+    
+    if (!roles) return false;
+    
+    return roles.some(r => ADMIN_ROLES.includes(r.role?.toLowerCase()));
+  } catch {
+    return false;
+  }
+}
+
+export default async function handler(req: VercelRequest, res: VercelResponse) {
+  res.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
+  
+  const supabase = supabaseUrl && supabaseServiceRole 
+    ? createClient(supabaseUrl, supabaseServiceRole)
+    : null;
+
+  if (req.method === "GET") {
+    try {
+      if (supabase) {
+        const { data, error } = await supabase
+          .from("platform_settings")
+          .select("value")
+          .eq("key", "maintenance_mode")
+          .single();
+
+        if (!error && data) {
+          const isEnabled = data.value === true || data.value === "true";
+          maintenanceModeCache = isEnabled;
+          return res.json({ maintenance_mode: isEnabled });
+        }
+      }
+      
+      const envMaintenance = process.env.MAINTENANCE_MODE === "true";
+      return res.json({ maintenance_mode: maintenanceModeCache ?? envMaintenance });
+    } catch (e) {
+      const envMaintenance = process.env.MAINTENANCE_MODE === "true";
+      return res.json({ maintenance_mode: maintenanceModeCache ?? envMaintenance });
+    }
+  }
+
+  if (req.method === "POST") {
+    const authHeader = req.headers.authorization;
+    const token = authHeader?.replace("Bearer ", "");
+
+    if (!token) {
+      return res.status(401).json({ error: "Unauthorized" });
+    }
+
+    const isAdmin = await verifyAdmin(token);
+    if (!isAdmin) {
+      return res.status(403).json({ error: "Forbidden - Admin access required" });
+    }
+
+    const { maintenance_mode } = req.body;
+
+    if (typeof maintenance_mode !== "boolean") {
+      return res.status(400).json({ error: "maintenance_mode must be a boolean" });
+    }
+
+    try {
+      if (supabase) {
+        const { error } = await supabase
+          .from("platform_settings")
+          .upsert(
+            { key: "maintenance_mode", value: maintenance_mode, updated_at: new Date().toISOString() },
+            { onConflict: "key" }
+          );
+
+        if (error) {
+          console.error("[Maintenance] DB error:", error);
+        }
+      }
+
+      maintenanceModeCache = maintenance_mode;
+      return res.json({ maintenance_mode, success: true });
+    } catch (e) {
+      maintenanceModeCache = maintenance_mode;
+      return res.json({ maintenance_mode, success: true });
+    }
+  }
+
+  return res.status(405).json({ error: "Method not allowed" });
+}