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-raid/src/raid/controller.rs

@@ -22,6 +22,12 @@ pub struct RaidController {
     arrays: Mutex<Vec<Arc<RaidArray>>>,
 }
 
+impl Default for RaidController {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl RaidController {
     pub fn new() -> Self {
         RaidController {