refactor+feat(backend): ChargeableCharConfig por ProductType + Reactivate + Delete endpoints (PRC-001)

Part A — MedioId → ProductTypeId rename across all C# layers:
  Domain, Application, Infrastructure, API, all test projects.
  Solution was non-compilable after BD refactor (5c1675e); now compiles clean (0 errors).

Part B — PATCH /api/v1/admin/chargeable-chars/{id}/reactivate:
  ReactivateChargeableCharConfigCommand/Handler, SP guard maps 50410/50411/50412
  → ChargeableCharConfigReactivationNotAllowedException(Reason) → HTTP 409.

Part C — DELETE /api/v1/admin/chargeable-chars/{id}:
  DeleteChargeableCharConfigCommand/Handler, physical DELETE on SYSTEM_VERSIONED table.
  KeyNotFoundException → 404 via ExceptionFilter.

Tests: +30 unit tests (TDD RED→GREEN). All 1266 unit tests pass.

src/api/SIGCM2.Application/Pricing/ChargeableChars/IChargeableCharConfigService.cs

@@ -1,21 +1,21 @@
 namespace SIGCM2.Application.Pricing.ChargeableChars;
 
 /// <summary>
-/// PRC-001 — Application service for resolving active chargeable-char config for a Medio.
+/// PRC-001 — Application service for resolving active chargeable-char config for a ProductType.
 ///
-/// Priority rule: per-medio row overrides global (MedioId IS NULL) for the same Symbol.
+/// Priority rule: per-ProductType row overrides global (ProductTypeId IS NULL) for the same Symbol.
 /// Returns a dictionary keyed by Symbol for O(1) lookup during word-count pricing.
 /// </summary>
 public interface IChargeableCharConfigService
 {
     /// <summary>
-    /// Returns the resolved active config for the given medio as of the given date.
-    /// Per-medio rows take priority over global rows for the same Symbol.
-    /// Global rows are used as fallback when no per-medio row exists for that Symbol.
+    /// Returns the resolved active config for the given ProductType as of the given date.
+    /// Per-ProductType rows take priority over global rows for the same Symbol.
+    /// Global rows are used as fallback when no per-ProductType row exists for that Symbol.
     /// Returns an empty dictionary if no config exists at all.
     /// </summary>
-    Task<IReadOnlyDictionary<string, ChargeableCharSnapshot>> GetActiveConfigForMedioAsync(
-        long medioId,
+    Task<IReadOnlyDictionary<string, ChargeableCharSnapshot>> GetActiveConfigForProductTypeAsync(
+        long productTypeId,
         DateOnly asOf,
         CancellationToken ct = default);
 }