feat(db): guilds, guild_members, guild_invites and guild_events

Four tables (MySQL migration 97, SQLite 80) and the IGuilds interface with MySQL, SQLite and TestSQL implementations,
for the guild system (docs/Guilds.md). A guild has a name (unique without regard to case), a name status like
pet_names (1 waiting for moderation, 2 approved), its founder and when it was made. A character is in at most one guild
(guild_members, with its rank: 1 leader, 2 officer, 3 veteran, 4 recruit, the client's names, and when it joined) and
has at most one pending invite (guild_invites). guild_events is each guild's history and outlives the guild. Deleting a
character removes its membership and the invites to and from it. Nothing uses the tables yet.

Check: both migrations run on a fresh and an existing database; DatabaseParityTests Guilds passes against MariaDB
(DLU_TEST_MYSQL_HOST) and SQLite gives the same results. Nothing to check in game.

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

migrations/dlu/sqlite/80_guilds.sql

@@ -0,0 +1,36 @@
+/* Guilds, owned by the chat server. See the MySQL migration. */
+CREATE TABLE IF NOT EXISTS guilds (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL COLLATE NOCASE UNIQUE,
+    name_status INTEGER NOT NULL DEFAULT 1,
+    founder_id BIGINT NOT NULL DEFAULT 0,
+    created_at BIGINT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS guild_members (
+    character_id BIGINT NOT NULL PRIMARY KEY,
+    guild_id BIGINT NOT NULL,
+    guild_rank INTEGER NOT NULL,
+    joined_at BIGINT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS guild_members_guild ON guild_members (guild_id);
+
+CREATE TABLE IF NOT EXISTS guild_invites (
+    character_id BIGINT NOT NULL PRIMARY KEY,
+    guild_id BIGINT NOT NULL,
+    inviter_id BIGINT NOT NULL,
+    created_at BIGINT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS guild_invites_guild ON guild_invites (guild_id);
+
+CREATE TABLE IF NOT EXISTS guild_events (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    guild_id BIGINT NOT NULL,
+    time BIGINT NOT NULL,
+    kind TEXT NOT NULL,
+    character_id BIGINT NOT NULL DEFAULT 0,
+    character_name TEXT NOT NULL DEFAULT '',
+    actor TEXT NOT NULL DEFAULT '',
+    detail TEXT NOT NULL DEFAULT ''
+);
+CREATE INDEX IF NOT EXISTS guild_events_guild ON guild_events (guild_id, id);