Add the core, contest, storage and format layers

Frequencies, bands, modes, callsigns, grid squares and the country file live in
Nonemm.Core. Nonemm.Contests holds the scoring engine and CQ WW and CQ WPX.
Nonemm.Storage writes N1MM's DXLOG schema, and Nonemm.Formats writes Cabrillo
3.0 and reads and writes ADIF.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.Storage/ContestInstance.cs

@@ -0,0 +1,40 @@
+namespace Nonemm.Storage;
+
+/// One running of a contest in the log: the entry categories, the sent exchange
+/// and the number every contact in it carries.
+public sealed record ContestInstance
+{
+    public required int ContestNumber { get; init; }
+
+    public required string ContestName { get; init; }
+
+    public DateTime StartDate { get; init; }
+
+    public string SentExchange { get; init; } = "";
+
+    public string SubType { get; init; } = "";
+
+    public string OperatorCategory { get; init; } = "SINGLE-OP";
+
+    public string BandCategory { get; init; } = "ALL";
+
+    public string PowerCategory { get; init; } = "HIGH";
+
+    public string ModeCategory { get; init; } = "";
+
+    public string OverlayCategory { get; init; } = "";
+
+    public string StationCategory { get; init; } = "";
+
+    public string AssistedCategory { get; init; } = "NON-ASSISTED";
+
+    public string TransmitterCategory { get; init; } = "ONE";
+
+    public string TimeCategory { get; init; } = "";
+
+    public string Operators { get; init; } = "";
+
+    public string Soapbox { get; init; } = "";
+
+    public long ClaimedScore { get; init; }
+}