Apply clippy fixes for code quality

Clippy Fixes Applied:
- Removed unused imports
- Fixed manual implementation of .is_multiple_of()
- Fixed unnecessary_sort_by suggestions
- Added missing Ipv4Addr imports

Files Modified:
- forward_acl.rs: Add Ipv4Addr import
- known_hosts.rs: Add Ipv4Addr import
- Various files: Remove unused imports

Build: ✅ markbase-core
Tests: 495 passed

markbase-core/src/vfs/checksum.rs

@@ -6,14 +6,13 @@
 //!
 //! MarkBase uses SHA-256 (32 bytes) per 4KB block for integrity verification.
 
-use std::collections::{HashMap, HashSet};
 use std::path::PathBuf;
-use std::io::{Read, Write, Seek, SeekFrom};
+use std::io::{Read, Write};
 
 use sha2::{Sha256, Digest};
 use serde::{Serialize, Deserialize};
 
-use super::{VfsBackend, VfsFile, VfsError, VfsStat};
+use super::{VfsBackend, VfsFile, VfsError};
 
 pub const BLOCK_SIZE: usize = 4096;
 pub const HASH_SIZE: usize = 32;  // SHA-256
@@ -71,7 +70,7 @@ impl VfsChecksumFile {
 
     pub fn block_count(&self) -> usize {
         (self.file_size as usize / BLOCK_SIZE) + 
-            if self.file_size as usize % BLOCK_SIZE > 0 { 1 } else { 0 }
+            if !(self.file_size as usize).is_multiple_of(BLOCK_SIZE) { 1 } else { 0 }
     }
 }
 
@@ -214,7 +213,7 @@ pub fn scrub_file(
             corrupted_blocks.push(offset);
             
             if repair {
-                if let Ok(_) = repair_block(backend, file_path, offset, &buffer) {
+                if repair_block(backend, file_path, offset, &buffer).is_ok() {
                     repaired_blocks.push(offset);
                 }
             }
@@ -283,10 +282,10 @@ fn scrub_recursive(
 ///
 /// Tries RAID repair first (if backend is RAID), then Dedup repair.
 pub fn repair_block(
-    backend: &dyn VfsBackend,
-    file_path: &PathBuf,
-    offset: u64,
-    expected_checksum: &[u8],
+    _backend: &dyn VfsBackend,
+    _file_path: &PathBuf,
+    _offset: u64,
+    _expected_checksum: &[u8],
 ) -> Result<Vec<u8>, VfsError> {
     // Try Dedup repair first (check if block exists in dedup store)
     // This requires the backend to have dedup integration