fix: resolve overlapping route and deprecated base64 decode usage

Co-authored-by: aider (openai/andrew/openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

src/modes/server/common.rs

@@ -5,6 +5,7 @@ use axum::{
     middleware::Next,
     response::Response,
 };
+use base64::Engine;
 use log::{info, warn};
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
@@ -80,7 +81,7 @@ fn check_basic_auth(auth_str: &str, expected_password: &str) -> bool {
     }
     
     let encoded = &auth_str[6..];
-    if let Ok(decoded_bytes) = base64::decode(encoded) {
+    if let Ok(decoded_bytes) = base64::engine::general_purpose::STANDARD.decode(encoded) {
         if let Ok(decoded_str) = String::from_utf8(decoded_bytes) {
             let expected_credentials = format!("keep:{}", expected_password);
             return decoded_str == expected_credentials;