fix: crash bugs in TeamInvoices + faster load

Bug fixes:
- TeamInvoices: add useAuth import/currentUser (invoice-create crash)
- TeamInvoices: setChartYear -> setExportYear (year-dropdown crash)
- TeamDashboard: drop redundant setState-in-effect (cascading renders)
- Companies: delete dead _UnusedClientCompanies (illegal hook calls)
- annotate intentional empty PDF-fallback catches

Load speed:
- preconnect/dns-prefetch to Supabase origin
- lazy-load heic-to in Converters: page chunk 2737KB -> 9KB
- split recharts into its own 'charts' vendor chunk

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/pages/PayInvoice.jsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from 'react';
 import { useParams, useSearchParams } from 'react-router-dom';
+import PageLoader from '../components/PageLoader';
 
 const supabaseUrl = import.meta.env.VITE_SUPABASE_URL;
 const supabaseAnonKey = import.meta.env.VITE_SUPABASE_ANON_KEY;
@@ -74,15 +75,14 @@ export default function PayInvoice() {
 
   return (
     <div style={{ minHeight: '100vh', background: '#f5f5f5', display: 'flex', flexDirection: 'column', alignItems: 'center', justifyContent: 'center', padding: 24 }}>
+      {loading ? <PageLoader /> : null}
       <div style={{ width: '100%', maxWidth: 480 }}>
         {/* Logo */}
         <div style={{ textAlign: 'center', marginBottom: 32 }}>
           <img src="/fourge-logo.png" alt="Fourge Branding" style={{ height: 36, filter: 'invert(1)' }} />
         </div>
 
-        {loading ? (
-          <div style={{ textAlign: 'center', color: '#666' }}>Loading...</div>
-        ) : !invoice ? (
+        {!invoice ? (
           <div style={{ background: '#fff', color: '#141414', borderRadius: 4, padding: 32, textAlign: 'center', boxShadow: '0 2px 12px rgba(0,0,0,0.08)' }}>
             <div style={{ fontSize: 18, fontWeight: 400, marginBottom: 8 }}>Invoice not found</div>
             <div style={{ color: '#666' }}>This payment link may be invalid or expired.</div>