Add cash management schema and immediate variance alerts

supabase/migrations/0015_midday_drops.sql

@@ -0,0 +1,70 @@
+-- =====================================================================
+-- Migration 0015 — Mid-Day Shift Cash Drops
+--
+-- Enables cashiers to "drop" large sums of accumulated cash (esp USD payout cash)
+-- into a safe midway through a shift, removing their liability without 
+-- requiring them to close out and open a brand new shift.
+-- =====================================================================
+
+create or replace function app.record_cash_drop(
+  p_shift_id uuid,
+  p_drop_usd numeric,
+  p_drop_lbp numeric,
+  p_notes text default null
+) returns void
+language plpgsql
+security definer
+set search_path = app, public
+as $$
+declare
+  v_shop uuid;
+  v_till uuid;
+  v_status text;
+  v_user uuid;
+begin
+  select shop_id, till_id, status, user_id
+    into v_shop, v_till, v_status, v_user
+    from app.shifts
+    where id = p_shift_id;
+    
+  if v_shop is null then
+    raise exception 'Shift not found';
+  end if;
+
+  if v_user <> auth.uid() and not app.has_role_in_shop(v_shop, 'manager') then
+    raise exception 'Only the shift owner or a manager may record a drop';
+  end if;
+  
+  if v_status <> 'open' then
+    raise exception 'Must have an open shift to record a soft drop';
+  end if;
+  
+  if p_drop_usd < 0 or p_drop_lbp < 0 then
+    raise exception 'Drop amounts cannot be negative';
+  end if;
+  
+  if p_drop_usd = 0 and p_drop_lbp = 0 then
+    raise exception 'Must drop > 0 in at least one currency';
+  end if;
+
+  -- Create a matching cash_movements record reducing the drawer balance
+  insert into app.cash_movements(
+    shift_id, movement_type, currency, amount, external_ref
+  )
+  select 
+    p_shift_id,
+    'safe_drop',
+    case when d.idx = 1 then 'USD' else 'LBP' end,
+    case when d.idx = 1 then p_drop_usd else p_drop_lbp end,
+    p_notes
+  from (values (1), (2)) as d(idx)
+  where (d.idx = 1 and p_drop_usd > 0)
+     or (d.idx = 2 and p_drop_lbp > 0);
+
+  perform app.log_auth_event('safe_drop_recorded', v_shop, null,
+                             jsonb_build_object('shift_id', p_shift_id, 'usd', p_drop_usd, 'lbp', p_drop_lbp));
+end;
+$$;
+
+revoke all on function app.record_cash_drop(uuid, numeric, numeric, text) from public;
+grant execute on function app.record_cash_drop(uuid, numeric, numeric, text) to authenticated;