feat(db): add guild_settings table for per-guild configuration

Store guild-specific settings (roles, channels, moderation options) in
database instead of config file, enabling per-guild configuration and
runtime updates without redeployment.

shared/db/schema/guild-settings.ts

@@ -0,0 +1,31 @@
+import {
+    pgTable,
+    bigint,
+    timestamp,
+    text,
+    jsonb,
+} from 'drizzle-orm/pg-core';
+import { relations, type InferSelectModel, type InferInsertModel } from 'drizzle-orm';
+
+export type GuildSettings = InferSelectModel<typeof guildSettings>;
+export type GuildSettingsInsert = InferInsertModel<typeof guildSettings>;
+
+export const guildSettings = pgTable('guild_settings', {
+    guildId: bigint('guild_id', { mode: 'bigint' }).primaryKey(),
+    studentRoleId: bigint('student_role_id', { mode: 'bigint' }),
+    visitorRoleId: bigint('visitor_role_id', { mode: 'bigint' }),
+    colorRoleIds: jsonb('color_role_ids').$type<string[]>().default([]),
+    welcomeChannelId: bigint('welcome_channel_id', { mode: 'bigint' }),
+    welcomeMessage: text('welcome_message'),
+    feedbackChannelId: bigint('feedback_channel_id', { mode: 'bigint' }),
+    terminalChannelId: bigint('terminal_channel_id', { mode: 'bigint' }),
+    terminalMessageId: bigint('terminal_message_id', { mode: 'bigint' }),
+    moderationLogChannelId: bigint('moderation_log_channel_id', { mode: 'bigint' }),
+    moderationDmOnWarn: jsonb('moderation_dm_on_warn').$type<boolean>().default(true),
+    moderationAutoTimeoutThreshold: jsonb('moderation_auto_timeout_threshold').$type<number>(),
+    featureOverrides: jsonb('feature_overrides').$type<Record<string, boolean>>().default({}),
+    createdAt: timestamp('created_at', { withTimezone: true }).defaultNow().notNull(),
+    updatedAt: timestamp('updated_at', { withTimezone: true }).defaultNow().notNull(),
+});
+
+export const guildSettingsRelations = relations(guildSettings, () => ({}));

shared/db/schema/index.ts

@@ -5,3 +5,4 @@ export * from './economy';
 export * from './quests';
 export * from './moderation';
 export * from './feature-flags';
+export * from './guild-settings';