feat(api): add staff order detail and compliance eligibility

docs/BACKEND/API_GUIDES/V2/staff-shifts.md

@@ -9,6 +9,7 @@ Base URL:
 ## Read routes
 
 - `GET /staff/orders/available`
+- `GET /staff/orders/:orderId`
 - `GET /staff/shifts/assigned`
 - `GET /staff/shifts/open`
 - `GET /staff/shifts/pending`
@@ -80,6 +81,7 @@ Example response:
 - booking is atomic across the future shifts in that order for the selected role
 - backend returns `PENDING` when the booking is reserved but not instant-booked
 - backend returns `CONFIRMED` when every future shift in that booking path is instant-booked
+- backend returns `422 UNPROCESSABLE_ENTITY` when the worker is not eligible to book that order
 
 Example request:
 
@@ -91,8 +93,44 @@ Example request:
 
 Important:
 
-- `roleId` for the order-booking flow is the role catalog id returned by `GET /staff/orders/available`
+- `GET /staff/orders/:orderId` is now the source of truth for the order detail screen before booking
+- `roleId` for the order-booking flow is the role catalog id returned by `GET /staff/orders/:orderId`
 - it is not the same thing as the per-shift `shift_roles.id`
+- when booking is rejected, use `details.blockers` from the error response to explain why
+
+### Order detail
+
+`GET /staff/orders/:orderId`
+
+Use this as the source of truth for the worker order-review page before calling `POST /staff/orders/:orderId/book`.
+
+Response shape includes:
+
+- `orderId`
+- `orderType`
+- `roleId`
+- `roleCode`
+- `roleName`
+- `clientName`
+- `businessId`
+- `instantBook`
+- `dispatchTeam`
+- `dispatchPriority`
+- `jobDescription`
+- `instructions`
+- `status`
+- `schedule`
+- `location`
+- `pay`
+- `staffing`
+- `managers`
+- `eligibility`
+
+Frontend rules:
+
+- call this endpoint after a worker taps an order card from `GET /staff/orders/available`
+- use the returned `roleId` when calling `POST /staff/orders/:orderId/book`
+- if `eligibility.isEligible` is `false`, show the blocker messages and disable booking
 
 ### Find shifts