fix: copy push notification processor to transaction baseClient

- Copy pushProcessor from parent client to transaction in newTx()
- Ensure transactions inherit push notification processor from parent client
- Prevent nil pointer dereference in transaction contexts (Watch, Unwatch, etc.)
- Maintain consistent push notification behavior across all Redis operations

This fixes the panic that was occurring in transaction examples where the
transaction's baseClient had a nil pushProcessor field, causing segmentation
violations during transaction operations like Watch and Unwatch.

Author: ndyakov

tx.go

@@ -24,9 +24,10 @@ type Tx struct {
 func (c *Client) newTx() *Tx {
 	tx := Tx{
 		baseClient: baseClient{
-			opt:        c.opt,
-			connPool:   pool.NewStickyConnPool(c.connPool),
-			hooksMixin: c.hooksMixin.clone(),
+			opt:           c.opt,
+			connPool:      pool.NewStickyConnPool(c.connPool),
+			hooksMixin:    c.hooksMixin.clone(),
+			pushProcessor: c.pushProcessor, // Copy push processor from parent client
 		},
 	}
 	tx.init()