Add categories and suppliers with CRUD routes

- category table with hierarchical parent_id, sort ordering, soft-delete
- supplier table with contact info, account number, payment terms
- CRUD routes for both with search on suppliers
- Zod validation schemas in @forte/shared
- Products will link to suppliers via join table (many-to-many)
- 26 tests passing

packages/backend/src/db/migrations/meta/_journal.json

@@ -29,6 +29,13 @@
       "when": 1774651222033,
       "tag": "0003_round_captain_midlands",
       "breakpoints": true
+    },
+    {
+      "idx": 4,
+      "version": "7",
+      "when": 1774652800605,
+      "tag": "0004_peaceful_wendell_rand",
+      "breakpoints": true
     }
   ]
 }