feat(api): 重构资产录入新增 exchange 字段，并接入腾讯财经 qt.gtimg 极速行情引擎

src/db/schema.ts

@@ -19,6 +19,7 @@ export const assets = pgTable("assets", {
   id: uuid("id").primaryKey().$defaultFn(() => crypto.randomUUID()),
   symbol: varchar("symbol", { length: 20 }).notNull().unique(),
   type: assetTypeEnum("type").notNull(),
+  exchange: varchar("exchange", { length: 10 }).default('US'),
   baseCurrency: varchar("base_currency", { length: 10 }).notNull(),
   latestPrice: numeric("latest_price", { precision: 36, scale: 18 }).default('0').notNull(),
   createdAt: timestamp("created_at", { withTimezone: true, mode: "date" })