Add IOTA, the EU DX Contest, CQ 160 and Mexico RTTY

Four more of the contests in the station's log. IOTA, CQ 160 and Mexico RTTY
score every contact in it exactly as N1MM did.

IOTA pays 15 points for a station that sends an island reference and 2 for one
that does not, and counts each reference once per band and mode. CQ 160 is one
band, so its states and countries count once each. Mexico RTTY and CQ 160 both
take a state from one side of the contest and a serial or a zone from the
other, in the columns N1MM keeps them in.

The EU DX Contest is written from N1MM's class, including its list of what
counts as Europe: the European Union, its outermost regions and its overseas
territories, and nothing else. The station's own logs were made with the .udc
file, which scores and counts two things differently; docs/unfinished.md says
which.

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

docs/unfinished.md

@@ -92,7 +92,7 @@ which is too much work per spot for the little it would add.
 the contest rules score it, but there is no digital window: no decoding, no
 transmitting, no interface to fldigi, MMTTY or similar.
 
-**Contest coverage.** Ten families are built in, plus whatever `.udc` files
+**Contest coverage.** Fourteen families are built in, plus whatever `.udc` files
 are in the user-defined folder. N1MM ships well over a hundred. Opening a log
 from a contest that is in neither place fails with the contest name, which is
 the right answer but it is still a wall.
@@ -123,11 +123,15 @@ a county from OK and OM stations and a serial number from everyone else — and
 of REF, ARRL 10M, the Ukrainian DX contest and the Russian DX contest, which
 are not written yet.
 
-What is left in the station's own logs, in the order it works them: IOTA, EU
-DXC, CQ 160, XE RTTY, REF, SARTG, BARTG, Field Day Region 1, Oceania, All
-Asian, RDAC and ARRL 10M. Everything but IOTA, REF and ARRL 10M is an exchange
-we already store — a serial, an age, a zone or a district — so a `.udc` file
-covers it.
+What is left in the station's own logs, in the order it works them: REF, the
+Ukrainian DX contest, SA-10, BARTG Sprint, ARRL 10M, Field Day Region 1, the
+Russian DX contest, RDAC, All Asian, YO HF DX and Oceania.
+
+The EU DX Contest is written from N1MM's own class. The station's logs were
+made with the `EU_DXC.udc` file instead, which scores a contact inside your own
+country 1 point where the class scores 2, and counts a district code once in
+the contest where the class counts it once per band. Those are the only
+differences left in those two logs.
 
 ## Known rough edges