Fix code quality: trailing whitespace, unused imports, clippy warnings

- Fix trailing whitespace in kex.rs and s3.rs
- Add missing KexProposal import in kex_complete.rs
- Auto-fix clippy warnings across all crates
- All 153 tests pass

markbase-iscsi/src/lib.rs

@@ -82,7 +82,7 @@ fn get_block_device_size(device: &str) -> Result<u64> {
     let stdout = String::from_utf8_lossy(&output.stdout);
     for line in stdout.lines() {
         if let Some(size_str) = line.strip_prefix("   Disk Size:") {
-            if let Some(bytes) = size_str.trim().split_whitespace().next() {
+            if let Some(bytes) = size_str.split_whitespace().next() {
                 if let Ok(size) = bytes.replace(',', "").parse::<u64>() {
                     return Ok(size);
                 }
@@ -120,7 +120,7 @@ pub fn generate_config(
         return Ok(());
     }
 
-    let (storage_path, lun_size_bytes) = if let Some(dev) = device {
+    let (storage_path, _lun_size_bytes) = if let Some(dev) = device {
         let dev_path = Path::new(dev);
         if !dev_path.exists() {
             anyhow::bail!("Block device not found: {}", dev);