DASP: drop the P-ION resend overrides, use standard 512-byte packets

The save and file-open requests used their own fixed resend intervals
(5 s / 15 s) and the hello asked for 256-byte packets. Ontrol's Sedona
Java stack does neither and works with the P-ION: the standard backoff
(1, 2, 4, 8 s) sends a busy device a few copies with the same seqNum,
which its receive window drops. Both are removed.

Also fixes a race in SendWindow.send(): the packet entered the window
before its payload and sent_time were set, so housekeeping could resend
it with an empty payload, and the device would then drop the real one
as a duplicate.

Tested on a P-ION at 192.168.1.252, App > Get with File: save 3.2 s
(2 resends), app.sab + kits.scode in 11.3 s with 500-byte chunks
(was 14.6 s at 256), device stayed up, files identical to a 256-byte
backup.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.144"
+VERSION = "0.0.0.145"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True