feat(09-01): add classification column to setupItems with service layer and tests

- Add classification text column (default 'base') to setupItems schema
- Add classificationSchema and updateClassificationSchema Zod validators
- Add UpdateClassification type inferred from Zod schema
- Implement updateItemClassification service function
- Modify getSetupWithItems to return classification field
- Modify syncSetupItems to preserve classifications across re-sync
- Add tests for classification CRUD, preservation, and cross-setup independence
- Generate and apply Drizzle migration

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

drizzle/0003_misty_mongu.sql

@@ -0,0 +1 @@
+ALTER TABLE `setup_items` ADD `classification` text DEFAULT 'base' NOT NULL;