fix: initialize seed and reset state in PYXXH32_new and PYXXH64_new

For consistency with XXH3_64 and XXH3_128 implementations, tp_new now
initializes self->seed = 0 and resets the internal state. This ensures
the object is in a valid state even if __init__ is bypassed (e.g. via
__new__ directly or subclassing without calling super().__init__).

Author: ifduyue

src/_xxhash.c

@@ -415,6 +415,9 @@ static PyObject *PYXXH32_new(PyTypeObject *type, PyObject *args, PyObject *kwarg
         return NULL;
     }
 
+    self->seed = 0;
+    XXH32_reset(self->xxhash_state, 0);
+
     return (PyObject *)self;
 }
 
@@ -719,6 +722,9 @@ static PyObject *PYXXH64_new(PyTypeObject *type, PyObject *args, PyObject *kwarg
         return NULL;
     }
 
+    self->seed = 0;
+    XXH64_reset(self->xxhash_state, 0);
+
     return (PyObject *)self;
 }