fix: clean up empty blocks and unused variables in backend utils

修复了后端工具文件中的空块和未使用的变量：
- auth-manager.ts: 移除空 else 块
- system-crypto.ts: 修复空 catch 块并添加注释
- starter.ts: 修复空 catch 块并添加注释
- server-stats.ts: 将未使用的 reject 参数重命名为 _reject
- credentials.ts: 将 connectionTimeout 从 let 改为 const

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/backend/database/routes/credentials.ts

@@ -1124,9 +1124,8 @@ async function deploySSHKeyToHost(
 ): Promise<{ success: boolean; message?: string; error?: string }> {
   return new Promise((resolve) => {
     const conn = new Client();
-    let connectionTimeout: NodeJS.Timeout;
 
-    connectionTimeout = setTimeout(() => {
+    const connectionTimeout = setTimeout(() => {
       conn.destroy();
       resolve({ success: false, error: "Connection timeout" });
     }, 120000);

src/backend/ssh/server-stats.ts

@@ -60,7 +60,7 @@ class SSHConnectionPool {
       return client;
     }
 
-    return new Promise((resolve, reject) => {
+    return new Promise((resolve, _reject) => {
       const checkAvailable = () => {
         const available = connections.find((conn) => !conn.inUse);
         if (available) {

src/backend/starter.ts

@@ -21,7 +21,9 @@ import { systemLogger, versionLogger } from "./utils/logger.js";
       if (persistentConfig.parsed) {
         Object.assign(process.env, persistentConfig.parsed);
       }
-    } catch {}
+    } catch {
+      // Ignore errors if .env file doesn't exist
+    }
 
     let version = "unknown";
 

src/backend/utils/auth-manager.ts

@@ -108,7 +108,6 @@ class AuthManager {
 
       if (migrationResult.migrated) {
         await saveMemoryDatabaseToFile();
-      } else {
       }
     } catch (error) {
       databaseLogger.error("Lazy encryption migration failed", error, {

src/backend/utils/system-crypto.ts

@@ -37,7 +37,9 @@ class SystemCrypto {
           process.env.JWT_SECRET = jwtMatch[1];
           return;
         }
-      } catch {}
+      } catch {
+        // Ignore file read errors, will generate new secret
+      }
 
       await this.generateAndGuideUser();
     } catch (error) {