test(18-02): add failing tests for global item service and seed

- 10 test cases covering search, owner count, link/unlink, seed idempotency
- Added globalItems/itemGlobalLinks tables to SQLite schema
- Added Zod schemas and types for global items
- Created 18-item bikepacking gear seed data JSON

src/db/schema.ts

@@ -127,6 +127,31 @@ export const apiKeys = sqliteTable("api_keys", {
 		.$defaultFn(() => new Date()),
 });
 
+export const globalItems = sqliteTable("global_items", {
+	id: integer("id").primaryKey({ autoIncrement: true }),
+	brand: text("brand").notNull(),
+	model: text("model").notNull(),
+	category: text("category"),
+	weightGrams: real("weight_grams"),
+	priceCents: integer("price_cents"),
+	imageUrl: text("image_url"),
+	description: text("description"),
+	createdAt: integer("created_at", { mode: "timestamp" })
+		.notNull()
+		.$defaultFn(() => new Date()),
+});
+
+export const itemGlobalLinks = sqliteTable("item_global_links", {
+	id: integer("id").primaryKey({ autoIncrement: true }),
+	itemId: integer("item_id")
+		.notNull()
+		.references(() => items.id, { onDelete: "cascade" })
+		.unique(),
+	globalItemId: integer("global_item_id")
+		.notNull()
+		.references(() => globalItems.id, { onDelete: "cascade" }),
+});
+
 export const oauthClients = sqliteTable("oauth_clients", {
 	id: integer("id").primaryKey({ autoIncrement: true }),
 	clientId: text("client_id").notNull().unique(),