backend phase 7: search & matching (nurse_search_index)

Add the discovery layer: the denormalized nurse_search_index read model
(one row per bookable variant x covered service area), maintained inline
inside each source write's transaction, plus the single public search
query behind the INurseSearch seam.

- Entity + EF config + migration (search schema): covering search index,
  filtered-unique (variant_id, city_id, district_id) pair with NULL
  district participating, nurse_id index, soft-delete.
- ISearchIndexMaintainer (write seam) + SearchIndexMaintainer: reindex
  variant / nurse / fan-out / remove-area / full rebuild, staged in the
  owning source write's unit of work; wired into the b3/b4/b5/b6 handlers.
- INurseSearch (read seam) + SqlNurseSearch (real MVP backend): reads only
  is_searchable=1, category/city/district(NULL-aware)/gender/price filters,
  rating sort, pagination. Elasticsearch deferred (config Search:Backend).
- SearchNursesQuery (+ validator) and RebuildSearchIndexCommand; public
  SearchController (GET search/nurses) + admin AdminSearchController
  (POST admin_search/rebuild_index).
- Tests: 9 DB-backed maintainer/search + 4 WebApplicationFactory; updated
  affected b3/b4/b5/b6 handler tests. Build clean, 167 tests green.
- Docs: server CLAUDE.md project map, contract search.md, swagger refresh,
  handoff, report, mocks-registry rows, STATUS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

dev/shared-working-context/backend/handoff/after-backend-phase-7.md

@@ -0,0 +1,50 @@
+# Handoff — after backend-phase-7 (Search & matching)
+
+**Search is live.** Verified nurses are now discoverable through one public endpoint backed by a
+denormalized, maintained-on-write index. This unblocks **frontend f6-b7**: search + filters (C1), results
+list (C2), and the nurse profile (C3) can be built against a real API.
+
+## What the frontend can now build (f6-b7)
+
+- **Search + filters (C1)** → `GET api/v1/search/nurses` (public, no auth). Query params (snake_case):
+  `service_category_id` (**required**), `city_id` (**required**), `district_id` (optional),
+  `nurse_gender` (`male`/`female`, optional), `min_price`/`max_price` (IRR long, optional),
+  `price_unit` (optional), `page`/`page_size` (default 1 / 50, max 100).
+- **Results list (C2)** → the `data` is a `PagedResult<NurseSearchResultDto>` (`items`, `total`, `page`,
+  `pageSize`). Each item: `variantId`, `nurseId`, `serviceCategoryId`, `price` (IRR **digit string**),
+  `priceUnit`, `nurseGender`, `averageRating`, `totalReviews`, `totalCompletedBookings`, `cityId`,
+  `districtId` (null = whole city).
+- **Nurse profile (C3)** → reuse the b6 public trust badge (`GET api/v1/nurses/{id}/trust_badge`) and the b5
+  public variant read (`GET api/v1/nurse_variants/get/{id}`) already live; b7 adds no new profile route.
+
+Categories/cities/districts for the filter dropdowns come from the **b4** geo lookups (`geo/*`) and **b5**
+catalog (`catalog/*`) — unchanged.
+
+## Rules the UI must respect
+
+- **Only searchable nurses come back.** The backend returns a nurse **only** when verified + not suspended +
+  accepting + variant active. No client-side re-check needed; an empty page is a valid result.
+- **`districtId = null` = whole city.** A city-only search returns both whole-city and district rows; a
+  district search returns that district's rows **plus** whole-city rows. Show whole-city hits as covering the
+  district the user searched.
+- **Same-gender filter is first-class.** Surface `nurse_gender` prominently; never default it silently.
+  (Carrying the chosen gender into the booking request — `required_caregiver_gender` — is **b8**, not here.)
+- **`price` is an IRR digit string** — render with a formatter; never parse to a float. Combine with
+  `priceUnit` (+ `sessionCount` from the variant, when booking) for the engagement total.
+- **Sort is rating-desc only** (MVP). No client sort options beyond what the API returns.
+
+## Contracts
+
+- New: [`dev/contracts/domains/search.md`](../../contracts/domains/search.md).
+- `swagger.v1.json` refreshed (adds `search/nurses` + `admin_search/rebuild_index` + the DTOs).
+
+## Backend notes (not frontend-facing)
+
+- The index is a **read-only projection** maintained inline inside each source write's transaction
+  (`ISearchIndexMaintainer`, wired into the b3/b4/b5/b6 handlers). The read seam is **`INurseSearch`**
+  (SQL now; Elasticsearch is a config-selected drop-in later, `Search:Backend`).
+- Admin `POST api/v1/admin_search/rebuild_index` (dynamic-permission) does an idempotent full rebuild — the
+  reconciliation path; incremental maintenance and rebuild converge.
+- **Deferred to b8:** `booking_requests.required_caregiver_gender` capture (carry the chosen gender into the
+  booking). **Deferred:** Elasticsearch backend + feeder, availability hard-filter, map/radius discovery,
+  ranking beyond rating.