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/20260608150000_remove_submission_signs_table.sql

@@ -0,0 +1,23 @@
+update public.submissions s
+set signs = legacy.signs
+from (
+  select
+    submission_id,
+    jsonb_agg(
+      jsonb_build_object(
+        'sign_number', sign_number,
+        'sign_name', sign_name,
+        'sign_family', sign_family
+      )
+      order by sign_number
+    ) as signs
+  from public.submission_signs
+  group by submission_id
+) as legacy
+where s.id = legacy.submission_id
+  and (
+    s.signs is null
+    or s.signs = '[]'::jsonb
+  );
+
+drop table if exists public.submission_signs cascade;