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/index.ts

@@ -19,6 +19,7 @@ import { impersonationRouter } from "./routes/impersonation.js";
 import { settingsRouter } from "./routes/settings.js";
 import { authProviderRouter } from "./routes/authProvider.js";
 import { searchRouter } from "./routes/search.js";
+import { bufferRulesRouter } from "./routes/buffer-rules.js";
 import { getObject } from "./lib/s3.js";
 import { calendarRouter } from "./routes/calendar.js";
 import { setupRouter } from "./routes/setup.js";
@@ -269,6 +270,7 @@ api.route("/admin/settings", settingsRouter);
 api.route("/admin/auth-provider", authProviderRouter);
 api.route("/admin/seed", adminSeedRouter);
 api.route("/search", searchRouter);
+api.route("/buffer-rules", bufferRulesRouter);
 
 const port = Number(process.env.PORT ?? 3000);
 await initAuth();