feat(GRO-1427): add buffer rules CRUD — enums, table, routes

Re-implement lost commit from worktree cleanup. PR #12 already has
UAT_PLAYBOOK + factories fix; add all missing core implementation:
- Add petSizeCategoryEnum/coatTypeEnum to schema
- Add bufferRules table with service FK + unique constraint
- Add defaultBufferMinutes column to services table
- Change pets.coatType/petSizeCategory text columns to use enums
- Add routes/buffer-rules.ts: GET/POST/PATCH/DELETE, manager role guard
- Register /api/buffer-rules in index.ts
- Update services.ts PATCH to accept defaultBufferMinutes
- Update pets.ts POST/PATCH to accept sizeCategory/coatType
- Cast coatType/petSizeCategory in book.ts insert to match new enums
- Add 0031_buffer_rules.sql migration
- Fix factories.ts buildService to include defaultBufferMinutes: null

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/routes/pets.ts

@@ -24,6 +24,8 @@ const createPetSchema = z.object({
   shampooPreference: z.string().max(500).optional(),
   specialCareNotes: z.string().max(2000).optional(),
   customFields: z.record(z.string(), z.string()).optional(),
+  sizeCategory: z.enum(["small", "medium", "large", "xlarge"]).optional(),
+  coatType: z.enum(["smooth", "double", "wire", "curly", "long", "hairless"]).optional(),
 });
 
 const updatePetSchema = createPetSchema.partial().omit({ clientId: true });