fix: integer overflow when inactive_time exceeds 35

When the inactive_time configuration value exceeds 35, the expression
`get_config().inactive_time * 60 * 1000 * 1000`
overflows the maximum int value due to implicit integer conversion.

src/bt.cpp

@@ -333,8 +333,8 @@ static void l2cap_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t
             }
             if (packet[3] < 120 || packet[3] > 140) {
                 inactive_time = get_absolute_time();
-            } else if (absolute_time_diff_us(inactive_time, get_absolute_time()) > get_config().inactive_time * 60 *
-                       1000 * 1000) {
+            } else if (absolute_time_diff_us(inactive_time, get_absolute_time()) >
+                       static_cast<int64_t>(get_config().inactive_time) * 60 * 1000 * 1000) {
                 printf("disconnect when inactive\n");
                 inactive_time = get_absolute_time();
                 bt_disconnect();