fix: invoice integrity — atomic numbering, safe delete, single create path

- Invoice numbers now come from DB function next_invoice_number()
  (max+1 per year under advisory lock) with a unique index; the old
  row-count method reused numbers after deletes and raced concurrent
  creates, which broke public pay links
- Remove dead standalone TeamCreateInvoice page; the TeamInvoices
  modal is the single create path (page had already drifted)
- Invoice delete now asks for confirmation and only un-bills tasks/
  submissions not billed on another invoice
- Created invoice shows correct "sent" status in list without reload
- Invoice/due dates computed at save time, not module load
- Reopening a paid invoice clears stale stripe_fee
- Stripe webhook markPaid is idempotent (no double receipts)
- subcontractor_invoice_items.version_number column stores billing
  version explicitly; description parsing kept as legacy fallback
- Drop unused buildInvoiceStatusByKey/deriveVersionStatus

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

supabase/migrations/20260612021739_remote_history_placeholder.sql

@@ -0,0 +1 @@
+-- Applied remotely via MCP on 2026-06-12; placeholder to align migration history.

supabase/migrations/20260612100000_add_invoice_number_fn.sql

@@ -0,0 +1,37 @@
+-- Invoice numbers were generated client-side from a row count, which reuses
+-- numbers after deletes and collides under concurrency. Replace with a DB
+-- function that takes max+1 for the year under an advisory lock, and enforce
+-- uniqueness at the schema level.
+
+create or replace function public.next_invoice_number()
+returns text
+language plpgsql
+security definer
+set search_path = public
+as $$
+declare
+  yr text := to_char(now(), 'YYYY');
+  next_n int;
+begin
+  -- Serialize concurrent invoice creation within this transaction
+  perform pg_advisory_xact_lock(hashtext('invoice_number_' || yr));
+
+  select coalesce(
+    max((regexp_match(invoice_number, '^INV-' || yr || '-(\d+)$'))[1]::int),
+    0
+  ) + 1
+  into next_n
+  from public.invoices
+  where invoice_number like 'INV-' || yr || '-%';
+
+  return 'INV-' || yr || '-' || lpad(next_n::text, 3, '0');
+end;
+$$;
+
+revoke all on function public.next_invoice_number() from public;
+grant execute on function public.next_invoice_number() to authenticated;
+
+-- Enforce uniqueness going forward (fails if historical duplicates exist —
+-- those must be reviewed manually first, never auto-renumbered).
+create unique index if not exists invoices_invoice_number_key
+  on public.invoices (invoice_number);

supabase/migrations/20260612100001_add_version_number_to_sub_invoice_items.sql

@@ -0,0 +1,7 @@
+-- Sub-invoice billing version was only recoverable by parsing "– R01" out of
+-- the free-text item description, which breaks the moment anyone edits the
+-- text. Store the version explicitly on new rows; existing rows stay null and
+-- readers fall back to the description parser for them.
+
+alter table public.subcontractor_invoice_items
+  add column if not exists version_number integer;