Read the .udc CallHist multiplier and BonusPoints2

MultSqlString = CallHist counts every station the call history file
lists, once per callsign, which is how N1MM dedups it. The file reaches
the scoring code through ContestLog.History, and a QsoContext now
carries it; without a file loaded nothing counts.

BonusPoints2 = +50, calls.txt reads the callsigns from the support-files
folder and adds 50 to the contact, *2 doubles it and a plain 50 scores
50 instead. The folder comes from the registry, which the app passes
when it reads the .udc files. N1MM's other form, where the file is
grids.txt and the bonus is looked up by grid square, is not read.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RoGtneMQaz4M9w7Kk49AVD

docs/unfinished.md

@@ -108,11 +108,10 @@ needs QTC traffic, IOTA needs island references as multipliers, and CQ WW RTTY
 needed a third multiplier and its own points table because it shares a name
 with the CW and SSB running of the contest.
 
-`.udc` settings that are still passed over. `CallHist` as a multiplier source,
-which takes the value from the call history file. `BonusPoints2`, which reads
-the bonus callsigns from a file. `MultiplierBands` and `QsoErrorString`, which
-are about the windows rather than the score. `GenericPrintString`, which is the
-layout of a printed log rather than a Cabrillo one.
+`.udc` settings that are still passed over. `MultiplierBands` and
+`QsoErrorString`, which are about the windows rather than the score.
+`GenericPrintString`, which is the layout of a printed log rather than a
+Cabrillo one.
 
 `MultWindowType` is read as far as the score goes: it names the list a section
 multiplier is checked against. Four of N1MM's lists are held here — the ARRL