refactor(db): split schema into domain modules

Split the 276-line schema.ts into focused domain modules:
- users.ts: classes, users, userTimers (core identity)
- inventory.ts: items, inventory (item system)
- economy.ts: transactions, itemTransactions (currency flow)
- quests.ts: quests, userQuests (quest system)
- moderation.ts: moderationCases, lootdrops (moderation)

Original schema.ts now re-exports from schema/index.ts for backward
compatibility. All existing imports continue to work.

shared/db/schema/quests.ts

@@ -0,0 +1,54 @@
+import {
+    pgTable,
+    bigint,
+    varchar,
+    serial,
+    text,
+    jsonb,
+    timestamp,
+    integer,
+    primaryKey,
+} from 'drizzle-orm/pg-core';
+import { relations, type InferSelectModel } from 'drizzle-orm';
+import { users } from './users';
+
+// --- TYPES ---
+export type Quest = InferSelectModel<typeof quests>;
+export type UserQuest = InferSelectModel<typeof userQuests>;
+
+// --- TABLES ---
+export const quests = pgTable('quests', {
+    id: serial('id').primaryKey(),
+    name: varchar('name', { length: 255 }).notNull(),
+    description: text('description'),
+    triggerEvent: varchar('trigger_event', { length: 50 }).notNull(),
+    requirements: jsonb('requirements').notNull().default({}),
+    rewards: jsonb('rewards').notNull().default({}),
+});
+
+export const userQuests = pgTable('user_quests', {
+    userId: bigint('user_id', { mode: 'bigint' })
+        .references(() => users.id, { onDelete: 'cascade' }).notNull(),
+    questId: integer('quest_id')
+        .references(() => quests.id, { onDelete: 'cascade' }).notNull(),
+    progress: integer('progress').default(0),
+    completedAt: timestamp('completed_at', { withTimezone: true }),
+}, (table) => [
+    primaryKey({ columns: [table.userId, table.questId] })
+]);
+
+// --- RELATIONS ---
+export const questsRelations = relations(quests, ({ many }) => ({
+    userEntries: many(userQuests),
+}));
+
+export const userQuestsRelations = relations(userQuests, ({ one }) => ({
+    user: one(users, {
+        fields: [userQuests.userId],
+        references: [users.id],
+    }),
+    quest: one(quests, {
+        fields: [userQuests.questId],
+        references: [quests.id],
+    }),
+}));