feat(oura): backfill the full history in resumable slices

Every Oura collection, workouts and heart rate included, is now read
back to the start of the account's history by a backfill that runs
through the shared integration lane in five-minute slices. Each
collection walks from the day the backfill began toward the past one
window at a time (ninety days, thirty for sleep, seven for heart rate)
and the progress note on the user row records after every window where
it got to, so a slice cut short by its budget, the lane or a rate limit
resumes there. A 429 ends the slice and the next one waits for the
Retry-After Oura named. Activity and sleep are walked first to learn
where history starts; the rest stop a week before it.

Heart rate streams a page at a time and keeps only the days it touched,
so memory stays flat however long the history is. A collection the
grant does not cover is a scope note, not a failure; the first slice of
the next chain asks again, and a connect clears the completion stamp so
a newly granted scope is read without walking anything twice.

The two columns arrive empty, so every existing connection is offered
the backfill at the next boot without reconnecting. Before anything
else the backfill retires the WALKING_RUNNING_DISTANCE rows earlier
syncs wrote from the equivalent walking distance and refolds their days;
an account that kept such rows after disconnecting is offered too.

src/__tests__/backfill-preserves-updated-at-guard.test.ts

@@ -106,6 +106,8 @@ const BACKFILL_STAMPS: Record<string, string> = {
     "marks the connection's one-shot as done; not a listed record",
   "src/lib/jobs/strava-backfill.ts > user":
     "stamps the account's backfill-completed marker",
+  "src/lib/jobs/oura-backfill.ts > user":
+    "writes the account's backfill progress note and completed marker",
   "src/lib/jobs/document-content-index-backfill.ts > documentContentIndex":
     "the index row is rebuilt content; its updatedAt is the rebuild time",
   "src/lib/jobs/lab-biomarker-backfill.ts > biomarker":

src/__tests__/measurement-write-tail-guard.test.ts

@@ -53,6 +53,8 @@ const WRITE_SITES: Record<string, string> = {
   "lib/whoop/webhook-handler.ts": TAIL,
   // Retiring the rows of Oura sleep periods the person rejected or deleted.
   "lib/oura/sync.ts": TAIL,
+  // Retiring the equivalent-distance rows earlier Oura syncs wrote.
+  "lib/oura/retire-distance.ts": TAIL,
   // Integration syncs: each collects the (type, day) pairs it touched and
   // runs both legs itself at the end of the sync.
   "lib/fitbit/sync-core.ts":