Closes #20358

- Adjust `recentIterateRange` DB query bounds to skip txNums already
covered by frozen files
- For ascending: raise the inclusive lower bound (`from`) to
`filesEndTxNum`
- For descending: raise the exclusive lower bound (`to`) to
`filesEndTxNum-1` (so `value > filesEndTxNum-1` ≡ `value >=
filesEndTxNum`)
- Add `TestInvertedIndex_IdxRange_SkipsFileRange`: builds files for 2
steps, prunes DB entries in the file range, verifies IdxRange still
returns correct results for both asc and desc

## Test plan
- [x] New test `TestInvertedIndex_IdxRange_SkipsFileRange` passes
- [x] All existing `TestInvIndex*` / `TestInvertedIndex*` tests pass
- [x] `make lint` clean
- [x] `make erigon integration` builds

- In `RangeAsOf`, the DB iterator (`HistoryRangeAsOfDB`) now starts from
`max(startTxNum, files.EndTxNum())` instead of `startTxNum` directly
- This avoids reading DB entries within the file range, which are
redundant (served by `HistoryRangeAsOfFiles`) and prunable
- Added `TestRangeAsOf_DBIteratorSkipsFileRange` to verify correctness
after pruning DB entries in the file range

Closes #20357

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Alex Sharov <AskAlexSharov@gmail.com>

…st (#20444)

Fixes #20355

- Skip DB entries whose step falls within the file range (`step.ToTxNum
< files.EndTxNum()`) in both the initial DB cursor push and the advance
loop — they are never loaded into the heap
- Matches the "don't query DB for data in files" pattern from #20360,
- Add `TestDomain_IteratePrefix_PrefersFilesOverDB` that simulates
partial lexicographic prune and verifies file values win

Follow-up: #20474 applies the same fix to
`DomainLatestIterFile.initCursorMDBX()` and `advanceInFiles()`

- [x] New test passes with fix, fails without it
- [x] `make lint` clean
- [x] `make erigon integration` builds

- Remove unused `step` parameter from the `IteratePrefix` callback
signature (interface, implementations, and all call sites)
- Remove `step` field from `CursorItem` struct (only used by
`debugIteratePrefixLatest`)
- Remove `step` field from `DomainDelPrefix` tombs tuple (was stored but
never read)
- Collapse step decode in DB cursor advancement to a single `endTxNum`
assignment