feat(chat): GuildManager, the guild rules of the chat server

The chat server is the guild authority (docs/Guilds.md). GuildManager keeps guilds in the database (IGuilds) and tells
clients through their worlds, with every outside dependency behind hooks so the rules are tested without a server:

- Create: name rules (3-30 of letters, digits, space ' - ., no space at either end or twice), the chat filter's deny
  list refuses a name (BAD_NAME), names not on the allow list make the guild but wait for moderation (other players see
  no guild name until then), a taken name (case ignored) is EXISTS, someone in a guild can't make one.
- Invite / answer: leaders and officers invite; the client's answers for not online, already in a guild, invite pending
  and could not invite; one invite per player, answerable for 10 minutes and gone when the player logs off; a full guild
  (guild_max_members) takes nobody. The new member is a recruit; the inviter hears the answer and gets the list again,
  the other members get GUILD_ADD_PLAYER.
- Leave, and DLU's kick, rank and disband (the client has no controls for them): the leader kicks anyone, officers kick
  veterans and recruits; a leader who leaves hands the guild to the highest-ranked, longest-serving member, and the last
  one out ends it. Rank changes send everyone the list again (the client's GuildSetPlayerRank does nothing).
- GUILD_DATA for GUILD_GET_ALL, login/logout/world-change updates to guildmates, a guild that lost its leader (character
  deleted) gets one again, and GuildChanged catches online players up with what the dashboard did.
- Every change is a guild_events row. Each character's world gets GUILD_GET_STATUS with the guild and the name others
  may see.

Not connected to the chat server's packets yet.

Check: GuildManagerTests (18 tests) run every rule against an in-memory IGuilds. Nothing to check in game yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dCommon/GuildNameRules.h

@@ -0,0 +1,27 @@
+#ifndef GUILDNAMERULES_H
+#define GUILDNAMERULES_H
+
+#include <cstddef>
+#include <string>
+
+// What a guild name may be (docs/Guilds.md), for the chat server and the dashboard
+namespace GuildNameRules {
+	constexpr size_t MIN_LENGTH = 3;
+	constexpr size_t MAX_LENGTH = 30; // the client sends at most 30 characters
+
+	// MIN_LENGTH to MAX_LENGTH of A-Z a-z 0-9, space, ' - . with no space at either end and no two in a row
+	inline bool IsValid(const std::u16string& name) {
+		if (name.size() < MIN_LENGTH || name.size() > MAX_LENGTH) return false;
+		if (name.front() == u' ' || name.back() == u' ') return false;
+		for (size_t i = 0; i < name.size(); i++) {
+			const char16_t c = name[i];
+			const bool allowed = (c >= u'a' && c <= u'z') || (c >= u'A' && c <= u'Z') || (c >= u'0' && c <= u'9') ||
+				c == u' ' || c == u'\'' || c == u'-' || c == u'.';
+			if (!allowed) return false;
+			if (c == u' ' && i > 0 && name[i - 1] == u' ') return false;
+		}
+		return true;
+	}
+}
+
+#endif // GUILDNAMERULES_H