v0.17.5: Pass N kernel block-device fallback + per-range fixes

Direct-SATA BU40N + Dune Part Two UHD live testing exposed that the
v0.17.3 single-shot SCSI READ path matched 0/22 of the small bad-
sector LBAs that dd if=/dev/sr0 recovers on the same drive. This
release closes that gap and fixes adjacent bugs silently capping
recovery.

- /dev/sr0 pread fallback in Drive::read (Linux only): on SCSI READ
  Err, fall back to posix_fadvise(DONTNEED) + pread() against the
  corresponding block device. Kernel sr_mod runs ~5 internal retries
  with no per-attempt mid-layer escalation overhead — the mechanism
  behind dd's recovery advantage. End-to-end byte verification
  confirms the fallback path returns real disc data.

- Disc::patch per-range watchdog fix: MAX_RANGE_SECS was breaking
  'outer (one slow range killed the entire patch). Now skips to the
  next range. Pre-fix patch died after 4 sectors of range 1 of 47.

- Per-sector range budget: range_budget = sectors × 25 s, capped at
  1800 s. Replaces the flat 180 s/range that was unfair to medium
  ranges and pointlessly generous to single-sector ones.

- consecutive_failures resets per range. The wedge-exit detector is
  for stuck-on-one-range, not many-small-ranges-with-one-fail-each.

- Reverted inline 5× retry experiment (was hurting: each retry paid
  kernel SCSI escalation overhead). Restored READ_RECOVERY_TIMEOUT_MS
  to 60 s. The kernel-auto-retry pattern is now provided by sr0
  fallback.

Empirical: pass 1 recovered 94.6 MB / 11 s of main title (33 sr0
saves). Pass 2 added 0.6 MB. Remaining ~233 MB on the test disc
appears physically unrecoverable on this hardware.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libfreemkv"
-version = "0.17.3"
+version = "0.17.5"
 edition = "2024"
 rust-version = "1.86"
 license = "AGPL-3.0-only"