feat: cashier/counter reports, service-order & remission flows, Rached migration utils

- Add "Mis cortes de caja" report for cashiers/counters with sales detail.
- Cash register history scoped to own cuts for non-admin roles; new /register/<id>/sales endpoint.
- Remove dashboard from cashier menu; add Reports to cashier/counter.
- Service orders: assign mechanic, budget field, invoice flag, counter/cashier can add items/remissions, convert to remission.
- Remission notes module (UI, CSS, courier, counter remissions).
- Customer hard-delete and vehicle/customer linkage in workshop.
- POS: always show search results, compact payment grid, credit validation, tier pricing (5%/10%), ticket with customer/folio.
- Inventory: CSV template with sku_secondary, alias import.
- Rached migration scripts and DB migrations.
- Version-bump cached JS/CSS query strings.

Excludes local Rached session tokens/captures (rached_*.json / rached_*.txt).

pos/services/inventory_engine.py

@@ -230,6 +230,54 @@ def record_sale(conn, inventory_id, branch_id, quantity, sale_id=None, cost_at_t
     return op_id
 
 
+def record_reservation(conn, inventory_id, branch_id, quantity, sale_id=None,
+                       cost_at_time=None, remaining_stock=None):
+    """Reserve stock for a counter remission note (negative quantity).
+
+    The reserved quantity is deducted from available stock until the note is
+    paid or cancelled.
+    """
+    op_id = record_operation(
+        conn, inventory_id, branch_id, 'REMISSION_RESERVE', -abs(quantity),
+        reference_id=sale_id, reference_type='sale', cost_at_time=cost_at_time,
+        notes='Reserva por nota de remision'
+    )
+    invalidate_stock(inventory_id, branch_id)
+    invalidate_stock(inventory_id, None)
+
+    try:
+        remaining = remaining_stock if remaining_stock is not None else get_stock(conn, inventory_id, branch_id)
+        if remaining <= 0:
+            cur = conn.cursor()
+            cur.execute("SELECT part_number, name FROM inventory WHERE id = %s", (inventory_id,))
+            inv_row = cur.fetchone()
+            cur.close()
+            if inv_row:
+                from services.push_service import notify_owner
+                notify_owner(
+                    conn,
+                    'Stock en Cero',
+                    f'{inv_row[1] or inv_row[0]} se quedo sin existencias',
+                    '/pos'
+                )
+    except Exception:
+        pass
+
+    return op_id
+
+
+def release_reservation(conn, inventory_id, branch_id, quantity, sale_id=None, notes=None):
+    """Release a previous reservation (positive quantity)."""
+    result = record_operation(
+        conn, inventory_id, branch_id, 'REMISSION_RELEASE', abs(quantity),
+        reference_id=sale_id, reference_type='sale',
+        notes=notes or 'Liberacion de reserva de nota de remision'
+    )
+    invalidate_stock(inventory_id, branch_id)
+    invalidate_stock(inventory_id, None)
+    return result
+
+
 def record_return(conn, inventory_id, branch_id, quantity, sale_id=None, notes=None):
     """Record a customer return (positive quantity)."""
     result = record_operation(