P10-T02 — Community read ports and local cache

Status: LOCAL_DONE on codex/phase-10-functional-integration (phase PR #54 pending, second task push). Issue: #46 (slice 2 of 8 local; P10-T09 pilot stays deferred until G18/G09 and is not part of G10-LOCAL). No ANP path touched, no legacy enum rename, no backend change.

Slice acceptance (frozen before coding)

• T02 (this commit) — backend reads without removing ANP offline paths: domain BackendPriceGroups (wire GASOLINE_ADDITIVED, community stays null until P04, exact milli money) + BackendPriceHttpGateway / BackendPriceCacheRepository ports + 60s BackendPriceCacheRule (matches Cache-Control: public, max-age=60) + CommunityReadsConfig default OFF; application GetCommunityPriceGroupsUseCase (Disabled / Fresh+save / StaleCache-explicit / Unavailable); data Room backend_price_cache (key station|fuel, source/version/expiry) with explicit MIGRATION_4_5, OkHttp BackendStationPriceHttpClient, Room+HTTP impls, CommunityReadsFlagStore default OFF, preview base URL .invalid (P13 precedent, never resolves).

What changed

• domain/.../model/BackendPriceGroups.kt — official/group/groups with UUID + 7-value wire + milli validation.
• domain/.../repository/BackendPricePorts.kt — network-only vs cache-only ports.
• domain/.../rule/BackendPriceCacheRule.kt — TTL 60s, stale/fresh.
• domain/.../feature/CommunityReadsConfig.kt — DISABLED default.
• application/.../port/CommunityReadsFlagProvider.kt + usecase/community/GetCommunityPriceGroupsUseCase.kt.
• data/.../entity/BackendPriceCacheEntity.kt + dao/BackendPriceCacheDao.kt.
• AnpFuelDatabase v4→v5, MIGRATION_4_5, DatabaseModule, 5.json.
• data/.../remote/BackendPriceGroupsJsonCodec.kt (null-community refused) + BackendStationPriceHttpClient.kt (network-only).
• data/.../repository/BackendPriceRepositories.kt + preferences/CommunityReadsFlagStore.kt.
• RepositoryModule binds, CommunityModule preview URL, UseCaseModule wiring.
• Tests: 5 domain-model + 3 rule + 5 use-case (disabled/fresh/down-no-cache/down-stale/blank) + 3 codec + 2 HTTP (path/filter, down/empty) + 3 cache-repo + 1 migration-unit + 1 androidTest V4→V5 (vehicles/history preserved).

RED → GREEN

• RED proven by new symbols before implementation (same pattern as P10-T01): BackendPriceHttpGateway, BackendPriceCacheRule, GetCommunityPriceGroupsUseCase, BackendPriceCacheDao, BackendStationPriceHttpClient did not exist; new tests referenced them. GREEN after adding bounded adapters only.

Validation (exact commands, this host)

./gradlew :domain:test :application:test :data:testDebugUnitTest --no-daemon --rerun-tasks
./gradlew :app:testDebugUnitTest :app:assembleDebug --no-daemon
bash scripts/check-mobile.sh --static-only
git diff --check
bash scripts/scan-secrets.sh

Outcome: :domain:test + :application:test + :data:testDebugUnitTest green (incl. 22 new unit suites listed above); :app:testDebugUnitTest

• assembleDebug BUILD SUCCESSFUL (ANP screens unchanged); check-mobile --static-only ok; diff --check/secrets clean. Limits: :data:connectedDebugAndroidTest NOT run locally (no emulator); V4→V5 device migration test added for CI/phase exit. No backend change; no production URL invented.