Accounting: selectable-source / multi-line manual deposits

Deposits no longer force the credit side through Undeposited Funds — the
structural cause of negative Undeposited balances. A deposit can now credit any
account(s): interest income, a refund, an insurance reimbursement, cash straight
to the bank, etc.

- Schema: add accounting.deposit_lines (deposit_id, company_id, account_id,
  amount, memo) for the credit side, plus deposits.source_account_id as a
  single-source fallback. RLS mirrors deposits (staff + company member).
- post_deposit_gl: Dr bank for the total; Cr each deposit_lines row's account
  for its amount; no lines -> Cr source_account_id; neither -> Cr Undeposited
  Funds (backward compatible — existing deposits stay Dr Bank / Cr Undeposited).
  Remainder safety net keeps the entry balanced. New trg_acct_deposit_line_gl
  re-posts when lines change (header trigger fires before lines exist).
- Make Deposit page: GL-driven submit writes the deposit header + deposit_lines
  and marks selected payments deposited. Adds an "Other deposit lines" grid
  (account + amount + memo) alongside the existing Undeposited selection, with a
  running grand total and a soft guard against over-crediting Undeposited.
  Drops the old bank/Undeposited register-transaction inserts and manual balance
  pokes (never exercised in production; carried a money-in sign bug). Deposits
  are GL-only, consistent with the sync-created deposits already in the DB.

Verified Dr/Cr for single-source and multi-line scenarios against the live GL.

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

supabase/migrations/20260604130500_post_deposit_gl_multi_source.sql

@@ -0,0 +1,50 @@
+-- post_deposit_gl: credit the chosen source account(s) instead of always Undeposited.
+-- Debit the bank for the deposit total; credit each deposit_lines row's account for its
+-- amount; if there are no lines, credit source_account_id; if neither is set, fall back
+-- to Undeposited Funds (backward compatible with every existing deposit). The GL
+-- contract (one journal entry per deposit, cleared by external ref acmacc_dep) is
+-- otherwise unchanged.
+create or replace function accounting.post_deposit_gl(_deposit_id uuid)
+  returns void language plpgsql security definer set search_path to 'public', 'accounting' as $function$
+declare
+  d accounting.deposits%rowtype;
+  _je uuid;
+  _line_count int;
+  _line_sum numeric;
+  _remainder numeric;
+begin
+  select * into d from accounting.deposits where id = _deposit_id;
+  if not found then return; end if;
+  perform accounting._gl_clear(d.company_id, 'acmacc_dep', d.id::text);
+  if not accounting.gl_managed(d.company_id) then return; end if;
+  if coalesce(d.amount, 0) = 0 or d.bank_account_id is null then return; end if;
+
+  insert into accounting.journal_entries (company_id, date, description, reference, external_source, external_id)
+  values (d.company_id, d.date, coalesce(nullif(d.memo, ''), 'Deposit'), null, 'acmacc_dep', d.id::text)
+  returning id into _je;
+
+  -- Debit the bank for the full deposit total.
+  insert into accounting.journal_entry_lines (journal_entry_id, account_id, debit, credit, description)
+  values (_je, d.bank_account_id, d.amount, 0, 'Deposit');
+
+  select count(*), coalesce(sum(amount), 0) into _line_count, _line_sum
+  from accounting.deposit_lines where deposit_id = d.id;
+
+  if _line_count > 0 then
+    -- Credit each line's account for its amount.
+    insert into accounting.journal_entry_lines (journal_entry_id, account_id, debit, credit, description)
+    select _je, dl.account_id, 0, dl.amount, coalesce(nullif(dl.memo, ''), 'Deposit')
+    from accounting.deposit_lines dl where dl.deposit_id = d.id;
+    -- Safety net: if the lines don't cover the total, balance the remainder to
+    -- Undeposited Funds so the entry never posts unbalanced (UI keeps them equal).
+    _remainder := d.amount - _line_sum;
+    if _remainder > 0.005 then
+      insert into accounting.journal_entry_lines (journal_entry_id, account_id, debit, credit, description)
+      values (_je, accounting.coa_undeposited(d.company_id), 0, _remainder, 'Deposit');
+    end if;
+  else
+    -- No lines: single-source deposit. Credit source_account_id, else Undeposited Funds.
+    insert into accounting.journal_entry_lines (journal_entry_id, account_id, debit, credit, description)
+    values (_je, coalesce(d.source_account_id, accounting.coa_undeposited(d.company_id)), 0, d.amount, 'Deposit');
+  end if;
+end$function$;