fix: close release preflight gaps

Route public health checks to the API, backfill and synchronize job opportunities, stabilize SPA smoke tests, and document operator-only production steps.

docs/decisions/ADR-002-job-application-model.md

@@ -50,6 +50,10 @@ Split `Job` from `JobApplication`, **additively and in stages**. Phase 0 lays th
 
 This keeps Phase 0 a pure schema-and-vocabulary change with **zero behavioural change** to existing workflows, which is what "unblock future phases safely" requires.
 
+### Phase 1 status (2026-07-31)
+
+Create and update paths now synchronize `Job`, and startup idempotently backfills a linked `Job` for every legacy application missing one. Reads and legacy columns remain unchanged until the production validation and observation release in `docs/operations/job-opportunity-cutover.md` complete.
+
 ### The invariant
 
 > `DateApplied` is set **if and only if** the job has left the pre-application stages.
@@ -94,8 +98,8 @@ EF emits a warning that the `SavedAt` backfill `UPDATE` runs while a rebuild of
 
 ## Phase 1 cutover plan
 
-1. Dual-write `Job` on every create path (`JobApplicationsController.Create`, `GmailController`'s job creation, CSV import).
-2. Backfill one `Job` per existing `JobApplication`; link via `JobId`.
+1. **Done:** dual-write `Job` on every persistence path (`JobApplicationsController` and Gmail suggestion creation; CSV import is preview-only).
+2. **Done:** backfill one `Job` per existing `JobApplication`; link via `JobId`.
 3. Flip reads to `Job`, one endpoint at a time.
 4. Drop the duplicated opportunity columns from `JobApplication`.
 5. Make `JobId` non-nullable.