Add first-run wizard with three privacy profiles

Fresh installs now open a setup window on first plugin load that
asks the user to pick one of three starting profiles. Existing
ChatTwo users keep skipping the wizard because the v6→v7 migration
sets Configuration.FirstRunCompleted = true on the same pass that
seeds the Privacy-First defaults — they already saw the migration
notification and can reopen the wizard from the Privacy tab if
they want to choose differently.

The three profiles map to concrete configuration sets:

  Privacy-First (recommended): own-conversation whitelist (30
  channels), retention enabled with the spec defaults (Tells 365
  days, own-conversation channels 90, fallback 30).

  Casual: Privacy-First plus public chat (Say/Shout/Yell, both
  emote types, Novice Network) with a 1-day retention window so
  RP players can scroll back the last scene without keeping
  third-party speech forever.

  Full History: filter off, retention off, GDPR warning shown
  inline. Behaves like upstream Chat 2.

The wizard window is non-modal but covers a wide layout (three
side-by-side cards) and closing it without picking anything is
treated as accepting whatever defaults are already in place. The
Privacy tab gains a "show wizard again" button at the top so the
choice is reversible.

ChatTwo/Privacy/PrivacyDefaults.cs

@@ -84,4 +84,28 @@ internal static class PrivacyDefaults
         [ChatType.ExtraChatLinkshell7] = 90,
         [ChatType.ExtraChatLinkshell8] = 90,
     };
+
+    // Casual profile = Privacy-First plus public chat (Say/Shout/Yell, both
+    // emote types, Novice Network), kept for a short 24-hour window so the
+    // last RP scene or shout trade is still searchable but third-party data
+    // doesn't accumulate forever.
+    internal static readonly IReadOnlySet<ChatType> CasualWhitelist = new HashSet<ChatType>(PrivacyFirstWhitelist)
+    {
+        ChatType.Say,
+        ChatType.Shout,
+        ChatType.Yell,
+        ChatType.CustomEmote,
+        ChatType.StandardEmote,
+        ChatType.NoviceNetwork,
+    };
+
+    internal static readonly IReadOnlyDictionary<ChatType, int> CasualRetentionOverrides = new Dictionary<ChatType, int>
+    {
+        [ChatType.Say] = 1,
+        [ChatType.Shout] = 1,
+        [ChatType.Yell] = 1,
+        [ChatType.CustomEmote] = 1,
+        [ChatType.StandardEmote] = 1,
+        [ChatType.NoviceNetwork] = 1,
+    };
 }