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

drizzle/meta/_journal.json

@@ -71,6 +71,13 @@
       "when": 1775287060443,
       "tag": "0009_happy_mockingbird",
       "breakpoints": true
+    },
+    {
+      "idx": 10,
+      "version": "6",
+      "when": 1775387093955,
+      "tag": "0010_demonic_rawhide_kid",
+      "breakpoints": true
     }
   ]
 }