1.3.0.35-dev6-cpr-vcodex-steroids

fix(library): align cover fallback with HomeActivity and add post-write validation

• Replicate HomeActivity's robust cover generation pattern in LibraryCache.
• Add mandatory post-generation BMP validation (parse headers, check dimensions)
  instead of blindly trusting the boolean return value of generateThumbBmp().
• Auto-remove corrupted or truncated (0-byte) BMP files to prevent retry loops
  from getting stuck on invalid ghost files.
• Add a double-attempt (fresh instance retry) for XTC cover generation to
  overcome transient heap fragmentation during page scans.
• Re-check contiguous heap (MaxAllocHeap) after full EPUB parsing and before
  image decoding to prevent OOM crashes on constrained devices.