feat(18-02): add global item routes, item link/unlink endpoints, and route tests

- GET /api/global-items with optional q search parameter
- GET /api/global-items/:id with ownerCount
- POST /api/items/:id/link to link user item to global item
- DELETE /api/items/:id/link to unlink
- Route registered in index.ts
- 10 route tests covering all endpoints

src/server/routes/global-items.ts

@@ -0,0 +1,30 @@
+import { Hono } from "hono";
+import { parseId } from "../lib/params.ts";
+import {
+	getGlobalItemWithOwnerCount,
+	searchGlobalItems,
+} from "../services/global-item.service.ts";
+
+type Env = { Variables: { db?: any } };
+
+const app = new Hono<Env>();
+
+app.get("/", (c) => {
+	const db = c.get("db");
+	const q = c.req.query("q");
+	const items = searchGlobalItems(db, q || undefined);
+	return c.json(items);
+});
+
+app.get("/:id", (c) => {
+	const db = c.get("db");
+	const id = parseId(c.req.param("id"));
+	if (!id) return c.json({ error: "Invalid global item ID" }, 400);
+
+	const item = getGlobalItemWithOwnerCount(db, id);
+	if (!item) return c.json({ error: "Global item not found" }, 404);
+
+	return c.json(item);
+});
+
+export { app as globalItemRoutes };