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>

supabase/migrations/20260603173000_prevent_paid_invoice_delete.sql

@@ -0,0 +1,19 @@
+-- Prevent deletion of paid client invoices for all roles.
+create or replace function public.prevent_paid_invoice_delete()
+returns trigger
+language plpgsql
+as $$
+begin
+  if old.status = 'paid' then
+    raise exception 'Paid invoices cannot be deleted.';
+  end if;
+  return old;
+end;
+$$;
+
+drop trigger if exists prevent_paid_invoice_delete on public.invoices;
+
+create trigger prevent_paid_invoice_delete
+before delete on public.invoices
+for each row
+execute function public.prevent_paid_invoice_delete();