feat(api): add staff order booking contract and shift timeline alias

docs/BACKEND/API_GUIDES/V2/README.md

@@ -7,7 +7,7 @@ This is the frontend-facing source of truth for the v2 backend.
 Frontend should call one public gateway:
 
 ```env
-API_V2_BASE_URL=https://krow-api-v2-933560802882.us-central1.run.app
+API_V2_BASE_URL=https://krow-api-v2-e3g6witsvq-uc.a.run.app
 ```
 
 Frontend should not call the internal `core`, `command`, or `query` Cloud Run services directly.
@@ -95,14 +95,12 @@ Source-of-truth timestamp fields include:
 
 - `startsAt`
 - `endsAt`
-- `startTime`
-- `endTime`
 - `clockInAt`
 - `clockOutAt`
 - `createdAt`
 - `updatedAt`
 
-Helper fields like `date` are UTC-derived helpers and should not replace the raw timestamp fields.
+Helper fields like `date`, `startTime`, and `endTime` are display helpers and should not replace the raw timestamp fields.
 
 ## 4) Attendance policy and monitoring