Add ENTRY_VOID movement type and integrate balance entry creation in invoice processing

- Introduced a new movement type 'ENTRY_VOID' to handle invoice reversals, ensuring net balance remains zero.
- Updated the FaLineItem DTOs to replace 'download' with 'discharge' for consistency.
- Implemented balance entry creation in the invoice processing and reverting workflows, enhancing inventory management.
- Adjusted progress tracking messages to reflect the new balance entry generation steps.

backend/api/v1/modules/a24/balance_movements/models.py

@@ -74,6 +74,12 @@ class MovementType(str, Enum):
     EXPIRATION = "expiration"            # Balance cancelled due to deadline
     REGIME_CHANGE_OUT = "regime_chg_out" # Eg. temporary → definitive (exit side)
 
+    # ── Reversal (annuls a prior ENTRY — used when un-processing an invoice) ─
+    # Inserting ENTRY_VOID with the same quantity as the original ENTRY leaves
+    # the net balance at zero, preventing any further discharges against that
+    # lot. A fresh ENTRY is created when the invoice is re-processed.
+    ENTRY_VOID = "entry_void"
+
 
 # Which movement types reduce the balance (sign = -1)
 NEGATIVE_MOVEMENTS = {
@@ -85,6 +91,7 @@ NEGATIVE_MOVEMENTS = {
     MovementType.TRANSFER_OUT,
     MovementType.EXPIRATION,
     MovementType.REGIME_CHANGE_OUT,
+    MovementType.ENTRY_VOID,
 }
 
 # Which types count toward "used" (CANTUSADA in Anexo 24 report)