refactor(bd): V023+V024 ChargeableCharConfig por ProductType + SP ReactivateWithGuard (PRC-001)

BREAKING: schema refactor pre-merge. Backend+frontend do not compile yet;
subsequent commits in this PR restore compilation. Acceptable only because
feature/PRC-001 is not yet merged to main.

- V023: drop MedioId + FK_Medio, add ProductTypeId + FK_ProductType, rename
  indexes, drop+create SPs InsertWithClose (now @ProductTypeId) and
  GetActiveForProductType (renamed from GetActiveForMedio). NEW SP
  ReactivateWithGuard (A+guard pattern for feature 3 of scope delta).
  Drop CK_Price_Positive, add CK_Price_NonNegative (>= 0 for opt-in billing).
- V024: reseed global rows with PricePerUnit = 0.0000 (opt-in billing).
- V023_ROLLBACK + V024_ROLLBACK scripts.
- SqlTestFixture: EnsureV023SchemaAsync, EnsureV024SeedAsync, renamed seed
  method signature (ProductTypeId=NULL + PricePerUnit=0), history table
  TablesToIgnore preserved. HardeningTests seeds dbo.ProductType (not Medio).
- MigrationTests: updated SP existence + column + FK + price assertions.
- RepositoryIntegrationTests + HardeningTests: SQL-level assertions updated;
  C# method/property renames deferred to Agent 2 (backend refactor).

database/migrations/V024_ROLLBACK.sql

@@ -0,0 +1,22 @@
+-- V024_ROLLBACK.sql
+-- PRC-001: Reversa de V024__reseed_global_with_zero_price.sql.
+--
+-- Restaura las 4 filas globales de seed a PricePerUnit = 1.0000 (valor original de V022).
+-- Solo ejecutar si V024 fue aplicado y se desea volver al estado previo.
+--
+-- Run on: SIGCM2 (dev), SIGCM2_Test_App, SIGCM2_Test_Api.
+
+SET QUOTED_IDENTIFIER ON;
+SET ANSI_NULLS ON;
+SET NOCOUNT ON;
+GO
+
+UPDATE dbo.ChargeableCharConfig
+   SET PricePerUnit = CAST(1.0000 AS DECIMAL(18,4))
+ WHERE ProductTypeId IS NULL
+   AND Symbol IN (N'$', N'%', N'!', N'¡')
+   AND ValidTo IS NULL;
+
+PRINT 'V024 ROLLBACK complete — global ChargeableCharConfig prices restored to 1.0000.';
+PRINT 'Rows updated: ' + CAST(@@ROWCOUNT AS NVARCHAR(10));
+GO