chore(config): align defaults with maintainer's live config

Three real-world adjustments to the default config that ships with a
fresh install:

- HellionThemeWindowOpacity 0.92 -> 0.5 so a fresh install lands at
  the more glass-like default the maintainer uses daily
- Use24HourClock false -> true to match a German / European locale.
  Works correctly thanks to the v0.5.1 strict-format fix that uses
  CultureInfo.InvariantCulture instead of the host culture
- HellionParty preset Channel: InputChannel.Party -> null. Auto-
  routing /party into a tab that also collects /alliance and /pvpteam
  surprises the user when they wanted to type into the other ones;
  the tab stays as a read surface

LoadPreviousSession and FilterIncludePreviousSessions stay false to
keep the privacy-strict 'every session starts fresh' line. The
maintainer's personal settings flip them on, but that's an
opt-in choice, not a default we should ship to every fresh install.
RetentionEnabled also stays false for the same opt-in reason.

ChatTwo/Util/TabsUtil.cs

@@ -108,7 +108,10 @@ public static class TabsUtil
             [ChatType.LootNotice] = (ChatSourceExt.All, ChatSourceExt.All),
             [ChatType.LootRoll] = (ChatSourceExt.All, ChatSourceExt.All),
         },
-        Channel = InputChannel.Party,
+        // No automatic input-channel switch; the Gruppe tab is a read
+        // surface that pulls in Party, CrossParty, Alliance and PvpTeam
+        // together. Auto-routing /party into this tab would surprise the
+        // user when they actually wanted /alliance or /pvpteam.
     };
 
     public static Tab HellionBeginner => new()