Configure Clock from TimeZone setting at startup

Program.cs

@@ -1,9 +1,15 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.AspNetCore.Authentication.Cookies;
 using NoticeBoard.Data;
+using NoticeBoard.Infrastructure;
 
 var builder = WebApplication.CreateBuilder(args);
 
+// Configure the shared "now" used for Meow expiry checks. Blank ("" or unset) keeps the
+// original behaviour (host machine's local time zone, e.g. IIS on a Windows Server set to
+// AEST). Docker's compose file sets this to "UTC" by default — see docker-compose.yml.
+Clock.Configure(builder.Configuration["TimeZone"]);
+
 // SQLite database. Defaults to the app's own directory (unchanged behaviour for IIS).
 // Set the "DataDirectory" setting (env var DataDirectory=... in Docker) to store the
 // database elsewhere — used by the Docker image so the DB lives on a mounted volume.