Add Stripe fee tracking on paid invoices + backfill function

- Store stripe_fee on invoices when webhook receives checkout.session.completed
- Display Stripe fee and net received in InvoiceDetail when paid via Stripe
- Add backfill-stripe-fees edge function to populate fee on existing paid invoices
- Migration: add stripe_fee column to invoices table
- Includes all pending portal changes (brand book, sign survey, task/project/company updates, etc.)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/email.js

@@ -1,8 +1,16 @@
 import { supabase } from './supabase';
 
 export async function sendEmail(type, to, data) {
-  const { error } = await supabase.functions.invoke('send-email', {
+  const { data: result, error } = await supabase.functions.invoke('send-email', {
     body: { type, to, data },
   });
-  if (error) console.error('Email error:', error);
+  if (error) {
+    console.error('Email invoke error:', error);
+    throw new Error(`Email failed: ${error.message || JSON.stringify(error)}`);
+  }
+  if (result?.error) {
+    console.error('Email send error:', result.error);
+    throw new Error(`Email failed: ${JSON.stringify(result.error)}`);
+  }
+  return result;
 }