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-smb/src/config.rs

@@ -34,7 +34,7 @@ impl SMBConfig {
             allow_users: vec!["accusys".to_string()],
         }
     }
-    
+
     pub fn to_smb_conf(&self) -> String {
         format!(
             "[{}]\n   path = {}\n   comment = {}\n   read only = {}\n   browseable = {}\n   valid users = {}\n",
@@ -46,4 +46,4 @@ impl SMBConfig {
             self.allow_users.join(", ")
         )
     }
-}
+}