main: change default polling intervals

The serial interface on the MD-01 seems to be extremely slow (this is
with USB serial, though the RS232 ports probably have the exact same
issue. It seems that sending requests too quickly may negatively
impact the performance of the controller/rotator (i.e. makes it shake
more)? I'm not exactly sure this is the correct conclusion, since our
timings do not compensate for the actual communication time with the
MD-01 (i.e. the 100ms poll rate sends the next request at least 100ms
after it has received a reply). However, based on empirical testing,
running these at a lower pace (perhaps particularly, the command
frequency?) seems to make a big difference in the amount of shake
observed. We will need to keep an eye on this over time.

src/main.zig

@@ -80,8 +80,8 @@ pub const RotInt = struct {
     offsets: AzEl = .{ .az = 0, .el = 0 },
     requested_posture: AzEl = .{ .az = 0, .el = 0 },
     current_posture: AzEl = .{ .az = 0, .el = 0 },
-    poll_interval: u64 = 100,
-    command_freq: u8 = 10,
+    poll_interval: u64 = 500,
+    command_freq: u8 = 4,
     pollcount: u9 = 0,
     state: State = .initial,