feat(calendar): add IGameCalendarService — UTC reset-boundary primitive

New config-driven service that replaces JstPeriod. All timestamps are UTC;
one config value (GameCalendarConfig.DailyResetUtcHour, default 0 = midnight
UTC) drives both ResetReady checks and DayKey/WeekKey/MonthKey bucket keys.
Because both derive from the same MostRecentBoundary helper, they can never
disagree.

Prod parity is a config flip: set DailyResetUtcHour=17 in GameConfigs to get
the 02:00 JST boundary. No JST-flavored math anywhere in the code.

JstPeriod callsite migration + deletion follow in subsequent commits.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Program.cs

@@ -127,6 +127,7 @@ public class Program
         builder.Services.AddScoped<IMatchContextBuilder, MatchContextBuilder>();
         builder.Services.AddScoped<IStoryService, StoryService>();
         builder.Services.AddScoped<ILoginBonusService, LoginBonusService>();
+        builder.Services.AddScoped<IGameCalendarService, GameCalendarService>();
         builder.Services.AddScoped<IDeckListBuilder, DeckListBuilder>();
         builder.Services.AddSingleton<IRandom, SystemRandom>();
         builder.Services.AddSingleton<PuzzleMissionEvaluator>();