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-nfs/src/main.rs

@@ -9,11 +9,11 @@ struct Cli {
     /// User ID (database name)
     #[arg(short, long)]
     user: String,
-    
+
     /// Database path
     #[arg(short, long, default_value = "data/users")]
     data_dir: String,
-    
+
     /// NFS server port
     #[arg(short, long, default_value_t = 11111)]
     port: u16,
@@ -21,19 +21,19 @@ struct Cli {
 
 fn main() -> anyhow::Result<()> {
     let cli = Cli::parse();
-    
+
     let db_path = PathBuf::from(&cli.data_dir).join(format!("{}.sqlite", cli.user));
-    
+
     if !db_path.exists() {
         eprintln!("Database not found: {}", db_path.display());
         eprintln!("Please create database first using markbase-core");
         return Err(anyhow::anyhow!("Database not found"));
     }
-    
+
     eprintln!("Starting MarkBase NFS server...");
     eprintln!("User: {}", cli.user);
     eprintln!("Database: {}", db_path.display());
     eprintln!("Port: {}", cli.port);
-    
+
     run_nfs_server(cli.user, db_path, cli.port)
-}
+}