Check the signal report before it goes in the log

The log window took any text in the two report columns. It now checks the
report the same way it checks the zone or the section: RST on most modes,
and a signal-to-noise ratio in decibels on FT8, FT4, JT65, Q65 and MSK144.
A WAE QTC row is skipped, because it keeps the time sent and the other
station's call in those two columns.

The grid column is checked on every contest now, not only when the contest
asks for a locator, and the value is stored as JN88dd.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015NZkFxHde1iifAQemFTHxf

src/Nonemm.Session/QsoField.cs

@@ -1,7 +1,8 @@
 namespace Nonemm.Session;
 
-/// A field of a logged contact that can be edited in the log window. The names
-/// match the log columns.
+/// A field of a logged contact the log window can show. Most can be edited;
+/// `Points` and `Multipliers` are worked out from the rules and are read only.
+/// The names match the log columns.
 public enum QsoField
 {
     Time,
@@ -29,4 +30,6 @@ public enum QsoField
     WpxPrefix,
     RadioNumber,
     RunPosition,
+    Points,
+    Multipliers,
 }