Closes#61.
## Summary
Permanently-blank Series (the half of #47 that creation-time acquisition cannot reach) heal on the next due poll cycle. The cover path is no longer kagane-only: every Site and both Libraries fill a blank Cover from the series page the chapter poll already fetched, and never replace a Cover that already exists.
## What changed
### `backend/internal/latest/poller.go`
- **`fillBlankCover`** — when `Cover` and `CoverAddress` are both blank, extract a source URL via `coverFrom` from the series-page body and store bytes through `SetSeriesCover`. Skips any Series that already has a source URL (owned by prefetch) or a stored address (never overwrite).
- **`prefetchCover`** — source-URL healing path, now site-uniform. Kagane no longer special-cases into `PutKaganeCover` alone; every Site lands on `SetSeriesCover`, so the wire Cover becomes a content-addressed public URL. Reuses already-stored bytes when present.
- **`storeCover` / `fetchCoverBytes`** — shared fetch+persist. Only kagane routes image bytes through the browser fetcher; every other Site uses plain TLS `CoverBytesFetch`. Failures log with the Series key and never return to the chapter path.
- **`checkOne`** — after a successful series-page fetch, calls `fillBlankCover` once regardless of whether chapter extraction succeeded (cover fill is independent of the chapter signal).
### `backend/internal/latest/poller_test.go`
Extended the existing poller harness (real store, fake fetchers) rather than a new one:
- `TestRunOnceFillsBlankCoverFromSeriesPage` — asura manga, lightnovelworld novel, kagane manga; asserts wire Cover + correct fetcher routing.
- `TestRunOnceDoesNotReplaceExistingCover` — second poll does not refetch.
- `TestRunOnceRetriesFailedBlankCoverOnNextPoll` — failed fill stays blank, next due cycle retries (no separate queue).
- `TestRunOnceBlankCoverFailureDoesNotBlockChapter` — chapter still lands; failure log carries the Series key.
- Kagane prefetch test now also asserts the content-addressed wire Cover.
## Acceptance criteria (#61)
| Criterion | Status |
|---|---|
| Cover prefetch runs for every Site | done |
| Cover prefetch runs for both Libraries | done |
| Poll fills a blank Cover | done |
| Poll never replaces an existing Cover | done |
| Failed cover fetch does not fail/block chapter poll | done |
| Failed cover fetch retried next poll, no separate queue | done |
| Failures logged with the Series | done |
| Existing poller tests extended | done |
| `go test ./...` green | done |
| Manually verified: blank Series gets Cover after a poll cycle | **left for you** |
## Out of scope / not closed
- Does **not** close#47 or #55 (per ticket).
- No migration/backfill script — the Poll walks every Series already.
- No admin refetch (#54).
## Review notes addressed
- Removed the kagane-only `PutKaganeCover` branch from prefetch so source-URL healing also sets `CoverAddress` (wire Cover).
- Guard so `fillBlankCover` does not double-fetch after `prefetchCover` healed the same snapshot.
- Single `fillBlankCover` call site after the series-page fetch.
## Test plan
- [x] `go test ./...` (backend; needs Docker/Postgres via `pgtest`)
- [ ] After deploy: pick a Series that was blank, wait one poll cycle, confirm Cover in web UI and userscript panel
Reviewed-on: #70
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>
sulthan
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