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/BrandBook.jsx

@@ -793,10 +793,11 @@ export default function BrandBook() {
         {loadingBooks ? (
           <p style={{ padding: '24px 0', color: 'var(--text-muted)' }}>Loading...</p>
         ) : filteredBooks.length === 0 ? (
-          <div className="empty-state">
-            <h3>{savedBooks.length === 0 ? 'No brand books yet' : 'No matching brand books'}</h3>
-            <p>{savedBooks.length === 0 ? 'Create your first brand book to get started.' : 'Try clearing the current company filter.'}</p>
-            <button className="btn btn-primary" onClick={handleNew} style={{ marginTop: 16 }}>+ New Brand Book</button>
+          <div className="card" style={{ minHeight: 160, display: 'flex', flexDirection: 'column', alignItems: 'center', justifyContent: 'center', gap: 12 }}>
+            <div style={{ fontSize: 13, color: 'var(--text-muted)', textAlign: 'center' }}>
+              {savedBooks.length === 0 ? 'No brand books' : 'No matching brand books'}
+            </div>
+            {savedBooks.length === 0 && <button className="btn btn-primary" onClick={handleNew}>+ New Brand Book</button>}
           </div>
         ) : (
           <div className="table-wrapper">