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-core/src/provider/sqlite.rs

@@ -1,7 +1,7 @@
-use std::path::PathBuf;
-use rusqlite::{Connection, params};
-use bcrypt::verify;
 use super::{DataProvider, ProviderError, User};
+use bcrypt::verify;
+use rusqlite::{params, Connection};
+use std::path::PathBuf;
 
 /// SQLite 数据提供者
 pub struct SqliteProvider {
@@ -13,7 +13,8 @@ impl SqliteProvider {
         let path = PathBuf::from(db_path);
         if !path.exists() {
             return Err(ProviderError::NotFound(format!(
-                "Database not found: {}", db_path
+                "Database not found: {}",
+                db_path
             )));
         }
         Ok(Self { db_path: path })
@@ -50,7 +51,8 @@ impl DataProvider for SqliteProvider {
             Ok(user) => Ok(Some(user)),
             Err(rusqlite::Error::QueryReturnedNoRows) => Ok(None),
             Err(e) => Err(ProviderError::Internal(format!(
-                "Database query error: {}", e
+                "Database query error: {}",
+                e
             ))),
         }
     }
@@ -66,7 +68,9 @@ impl DataProvider for SqliteProvider {
     }
 
     fn get_home_dir(&self, username: &str) -> Result<Option<String>, ProviderError> {
-        Ok(self.get_user(username)?.map(|u| u.home_dir.to_string_lossy().to_string()))
+        Ok(self
+            .get_user(username)?
+            .map(|u| u.home_dir.to_string_lossy().to_string()))
     }
 
     fn get_public_keys(&self, username: &str) -> Result<Vec<String>, ProviderError> {
@@ -98,7 +102,10 @@ mod tests {
     }
 
     fn get_test_db_path() -> String {
-        format!("{}/../data/auth.sqlite", std::env::var("CARGO_MANIFEST_DIR").unwrap())
+        format!(
+            "{}/../data/auth.sqlite",
+            std::env::var("CARGO_MANIFEST_DIR").unwrap()
+        )
     }
 
     #[test]