Implement shared authentication and authorization helpers for API security

Creates a new `api/_auth.ts` file containing functions for user authentication, role-based authorization, and compliance event logging, enhancing API security and access control.

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api/_auth.ts

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+import type { VercelRequest, VercelResponse } from "@vercel/node";
+import { createClient } from "@supabase/supabase-js";
+
+const SUPABASE_URL = process.env.VITE_SUPABASE_URL || process.env.SUPABASE_URL || "";
+const SUPABASE_ANON_KEY = process.env.VITE_SUPABASE_ANON_KEY || process.env.SUPABASE_ANON_KEY || "";
+const SUPABASE_SERVICE_ROLE = process.env.SUPABASE_SERVICE_ROLE || "";
+
+export interface AuthenticatedUser {
+  id: string;
+  email?: string;
+  user_type?: 'admin' | 'creator' | 'client' | 'staff' | 'user';
+  primary_arm?: string;
+}
+
+export interface AuthResult {
+  user: AuthenticatedUser | null;
+  error: string | null;
+  userClient: any | null;
+  adminClient: any | null;
+}
+
+export function getAdminClient() {
+  if (!SUPABASE_URL || !SUPABASE_SERVICE_ROLE) {
+    throw new Error("Supabase admin credentials not configured");
+  }
+  return createClient(SUPABASE_URL, SUPABASE_SERVICE_ROLE, {
+    auth: { autoRefreshToken: false, persistSession: false },
+  });
+}
+
+export function getUserClient(accessToken: string) {
+  if (!SUPABASE_URL || !SUPABASE_ANON_KEY) {
+    throw new Error("Supabase credentials not configured");
+  }
+  return createClient(SUPABASE_URL, SUPABASE_ANON_KEY, {
+    auth: { autoRefreshToken: false, persistSession: false },
+    global: {
+      headers: {
+        Authorization: `Bearer ${accessToken}`,
+      },
+    },
+  });
+}
+
+export async function authenticateRequest(req: VercelRequest): Promise<AuthResult> {
+  const authHeader = req.headers.authorization;
+  
+  if (!authHeader?.startsWith('Bearer ')) {
+    return { user: null, error: 'Unauthorized - Bearer token required', userClient: null, adminClient: null };
+  }
+  
+  const token = authHeader.split(' ')[1];
+  const adminClient = getAdminClient();
+  
+  const { data: { user }, error: authError } = await adminClient.auth.getUser(token);
+  
+  if (authError || !user) {
+    return { user: null, error: 'Invalid or expired token', userClient: null, adminClient: null };
+  }
+
+  const { data: profile } = await adminClient
+    .from('user_profiles')
+    .select('user_type, primary_arm')
+    .eq('id', user.id)
+    .single();
+
+  const userClient = getUserClient(token);
+
+  return {
+    user: {
+      id: user.id,
+      email: user.email,
+      user_type: profile?.user_type || 'user',
+      primary_arm: profile?.primary_arm,
+    },
+    error: null,
+    userClient,
+    adminClient,
+  };
+}
+
+export function requireAuth(result: AuthResult, res: VercelResponse): result is AuthResult & { user: AuthenticatedUser } {
+  if (result.error || !result.user) {
+    res.status(401).json({ error: result.error || 'Unauthorized' });
+    return false;
+  }
+  return true;
+}
+
+export function requireAdmin(result: AuthResult, res: VercelResponse): boolean {
+  if (!requireAuth(result, res)) return false;
+  if (result.user!.user_type !== 'admin') {
+    res.status(403).json({ error: 'Admin access required' });
+    return false;
+  }
+  return true;
+}
+
+export function requireRole(result: AuthResult, roles: string[], res: VercelResponse): boolean {
+  if (!requireAuth(result, res)) return false;
+  if (!roles.includes(result.user!.user_type || 'user')) {
+    res.status(403).json({ error: `Requires role: ${roles.join(' or ')}` });
+    return false;
+  }
+  return true;
+}
+
+export async function logComplianceEvent(
+  adminClient: any,
+  event: {
+    entity_type: string;
+    entity_id: string;
+    event_type: string;
+    event_category: 'compliance' | 'financial' | 'access' | 'data_change' | 'tax_reporting' | 'legal';
+    actor_id?: string;
+    actor_role?: string;
+    realm_context?: string;
+    description?: string;
+    payload?: Record<string, unknown>;
+    sensitive_data_accessed?: boolean;
+    financial_amount?: number;
+    legal_entity?: string;
+    cross_entity_access?: boolean;
+  },
+  req?: VercelRequest
+) {
+  return adminClient.from('nexus_compliance_events').insert({
+    ...event,
+    ip_address: req?.headers['x-forwarded-for']?.toString() || req?.socket?.remoteAddress,
+    user_agent: req?.headers['user-agent'],
+  });
+}
+
+export default async function handler(req: VercelRequest, res: VercelResponse) {
+  return res.status(501).json({ error: "Not a handler" });
+}