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/inventory.ts

@@ -0,0 +1,57 @@
+import {
+    pgTable,
+    bigint,
+    varchar,
+    serial,
+    text,
+    integer,
+    jsonb,
+    primaryKey,
+    check,
+} from 'drizzle-orm/pg-core';
+import { relations, sql, type InferSelectModel } from 'drizzle-orm';
+import { users } from './users';
+
+// --- TYPES ---
+export type Item = InferSelectModel<typeof items>;
+export type Inventory = InferSelectModel<typeof inventory>;
+
+// --- TABLES ---
+export const items = pgTable('items', {
+    id: serial('id').primaryKey(),
+    name: varchar('name', { length: 255 }).unique().notNull(),
+    description: text('description'),
+    rarity: varchar('rarity', { length: 20 }).default('C'),
+    type: varchar('type', { length: 50 }).notNull().default('MATERIAL'),
+    usageData: jsonb('usage_data').default({}),
+    price: bigint('price', { mode: 'bigint' }),
+    iconUrl: text('icon_url').notNull(),
+    imageUrl: text('image_url').notNull(),
+});
+
+export const inventory = pgTable('inventory', {
+    userId: bigint('user_id', { mode: 'bigint' })
+        .references(() => users.id, { onDelete: 'cascade' }).notNull(),
+    itemId: integer('item_id')
+        .references(() => items.id, { onDelete: 'cascade' }).notNull(),
+    quantity: bigint('quantity', { mode: 'bigint' }).default(1n),
+}, (table) => [
+    primaryKey({ columns: [table.userId, table.itemId] }),
+    check('quantity_check', sql`${table.quantity} > 0`)
+]);
+
+// --- RELATIONS ---
+export const itemsRelations = relations(items, ({ many }) => ({
+    inventoryEntries: many(inventory),
+}));
+
+export const inventoryRelations = relations(inventory, ({ one }) => ({
+    user: one(users, {
+        fields: [inventory.userId],
+        references: [users.id],
+    }),
+    item: one(items, {
+        fields: [inventory.itemId],
+        references: [items.id],
+    }),
+}));