fix(pvm): tie bridge to total by pricing variance at actual quantity

Symptom: the budget-to-actual bridge left a 480.00 residual, so the three
effects did not sum to the total revenue variance.
Root cause: price variance was measured at budget quantity, which strands the
price-times-volume interaction unassigned. Measuring price at actual quantity
folds that interaction into the price effect, and the bridge ties to zero.

Author: Vanithanallamothu

models/intermediate/int_pvm_components.sql

@@ -17,8 +17,9 @@ select
     actual_price,
     budget_revenue,
     actual_revenue,
-    -- price effect measured at budget quantity
-    cast((actual_price - budget_price) * budget_units as decimal(18,2)) as price_effect,
+    -- price effect measured at actual quantity, so the price-volume
+    -- interaction is captured here and the bridge ties out
+    cast((actual_price - budget_price) * actual_units as decimal(18,2)) as price_effect,
     -- quantity effect at budget price
     cast(budget_price * (actual_units - budget_units) as decimal(18,2)) as quantity_effect
 from s