Backlog: add GitHub production-data mirror (P3); mark API switch, unit tests, backoff done

BACKLOG.md

@@ -9,27 +9,8 @@ Status: TODO / IN PROGRESS / DONE / BLOCKED.
 
 ---
 
-## P0 — Next build
-
-- [ ] **Switch dataset to govuk API data** (BLOCKED on credentials)
-  Register at developer.fuel-finder.service.gov.uk (GOV.UK One Login / OAuth 2.0).
-  Relay already supports an OAuth provider upgrade path — `client_id`/`client_secret`
-  go into relay `.env`, never into the IPA. Live API replaces the hourly CSV mirror;
-  endpoint/schema mapping (E5/E10/DIESEL → FuelType) already proven in
-  `FuelPriceProvider.swift`. Until credentials arrive, the CSV mirror stays.
-  Any credentials received must be treated as secrets ([REDACTED] storage).
-
 ## P1 — Soon
 
-- [ ] **Unit test target for the app** — XCTest target covering:
-  - `FuelStore.sanitizedStationTitle` (title-case chunks, Sainsbury's apostrophe,
-    acronyms BP/MFG/ASDA/MOTO, hyphen/paren chunks, mixed-case passthrough)
-  - decode price guard: grades outside 50–500 pence/litre dropped
-    (`FuelPriceProvider.allPrices` + legacy `price` fallback)
-  - RAG thresholds (≤1.5p green / ≤4p amber / >4p red)
-  - Cheapest-vs-Closest sort + delta/TOP baseline (cheapest-within-radius both modes)
-  - miles→km and km→miles conversions (× 1.60934 / × 0.621371)
-- [ ] **Backlog hygiene** — mark implemented items DONE, prune obsolete entries
 - [ ] **EV charging?** — National Chargepoint Registry as a 4th "Charging" tab
   (second relay endpoint, ~40k+ UK chargers, OGL, connector-type filter) vs fuel-only.
 
@@ -52,6 +33,12 @@ Status: TODO / IN PROGRESS / DONE / BLOCKED.
 
 ## P3 — Ideas / Research
 
+- [ ] **Production data mirror (GitHub)** — relay pushes the synced dump
+  (`stations.json` + `latest.json` version pointer) to a PUBLIC GitHub repo; the
+  app fetches `raw.githubusercontent.com` with the LAN relay as fallback source.
+  Public repo required for App Review (reviewer must fetch the data themselves);
+  HTTPS/ATS fine; plain JSON data is not "remote code" (2.5.2-safe); bundle a small
+  fallback dump so the app never demos empty. Needs GitHub PAT (aptonline account).
 - [ ] **Fuel-price prediction** — trend from historical dumps (relay could keep a
   rolling archive) to show "price tends up/down".
 - [ ] **Price alerts for a specific station** — notify when a starred station's
@@ -63,6 +50,15 @@ Status: TODO / IN PROGRESS / DONE / BLOCKED.
 
 ## Done (recent)
 
+- [x] Switch dataset to govuk API data — official Fuel Finder OAuth API via
+  relay-api :8789 (source: api, ~8,012 stations); app baseURL → :8789; credentials
+  live in relay `.env` only, never in the IPA
+- [x] Unit test target for the app — FuelBoardShared XCTest target, 37 tests
+  (title sanitizer, decode price guard, RAG thresholds, cheapest/closest baseline,
+  miles↔km)
+- [x] Backlog hygiene — implemented items marked DONE, obsolete pruned
+- [x] Sync retry with exponential backoff — relay-api retries failed syncs
+  15s→15min cap; `/health` exposes retry state (`6a58275`)
 - [x] England-wide full-UK dump, on-device filtering (relay `142061b`, app `cf9765b`)
 - [x] Cache-first, 12 h gate, pull-to-refresh only
 - [x] Distance filter 5/10/15 miles, local-only changes (no re-fetch)