feat: add human-readable datetime formatting and !lastshow command

IRC plugins now format datetimes as "Wed Mar 11, 10:00 PM EDT" instead
of raw ISO 8601. Configurable timezone defaults to America/New_York.

Adds !lastshow N command to both Limnoria and Sopel plugins, returning
track N from the previous week's show via existing API endpoints.

Made-with: Cursor

plugins/limnoria/NtrPlaylist/config.py

@@ -34,3 +34,12 @@ conf.registerGlobalValue(
         """IRC nicknames allowed to run admin commands (space-separated).""",
     ),
 )
+
+conf.registerGlobalValue(
+    NtrPlaylist,
+    "displayTimezone",
+    registry.String(
+        "America/New_York",
+        """IANA timezone for displaying dates in IRC (e.g. America/New_York, America/Chicago).""",
+    ),
+)