Add Project Files section and show company name for external users on project detail

supabase/migrations/20260513210000_fix_sub_invoice_items_insert.sql

@@ -0,0 +1,8 @@
+-- Fix: items insert was blocked when invoice status = 'submitted' at creation time.
+-- Allow insert on own invoices regardless of status (ownership check is sufficient).
+drop policy if exists "Sub insert draft invoice items" on public.subcontractor_invoice_items;
+
+create policy "Sub insert own invoice items" on public.subcontractor_invoice_items
+  for insert with check (
+    invoice_id in (select id from public.subcontractor_invoices where profile_id = auth.uid())
+  );