fix: audit findings (typing, DTO, encryption, javadoc, service methods)

backend/src/main/java/com/srsystem/controller/EmployeeController.java

@@ -100,7 +100,7 @@ public class EmployeeController {
         return ResponseEntity.ok(ApiResponse.ok("직원이 등록되었습니다", created));
     }
 
-    @Operation(summary = "직원 정보 수정", description = "기본 정보(이름/이메일/전화번호/생년월일/학력/전공/졸업일/거주지/프로필사진) 수정")
+    @Operation(summary = "직원 정보 수정", description = "기본 정보(이름/이메일/전화번호/입사일/직급/프로필사진/사수) 수정")
     @PreAuthorize("hasRole('ADMIN')")
     @PutMapping("/{empId}")
     public ResponseEntity<ApiResponse<Employee>> update(

backend/src/main/java/com/srsystem/dto/EmployeeSearchResult.java

@@ -4,6 +4,7 @@ public record EmployeeSearchResult(
         Long empId,
         String name,
         String email,
-        String department
+        String roleCode,
+        String dispatchStatus
 ) {
 }

backend/src/main/java/com/srsystem/service/EmployeeService.java

@@ -75,6 +75,7 @@ public class EmployeeService {
                 e.getEmpId(),
                 e.getName(),
                 e.getEmail(),
+                e.getRoleCode() != null ? e.getRoleCode().name() : null,
                 e.getDispatchStatus() != null ? e.getDispatchStatus().name() : null
         );
     }

backend/src/main/java/com/srsystem/util/PhoneEncryptionConverter.java

@@ -21,8 +21,8 @@ public class PhoneEncryptionConverter implements AttributeConverter<String, Stri
     private static final int GCM_IV_LENGTH = 12;
     private static final int GCM_TAG_LENGTH = 128;
 
-    private static SecretKey secretKey;
-    private static final SecureRandom secureRandom = new SecureRandom();
+    private SecretKey secretKey;
+    private final SecureRandom secureRandom = new SecureRandom();
 
     public PhoneEncryptionConverter(@Value("${app.encryption.phone-key}") String key) {
         byte[] keyBytes = key.getBytes();
@@ -65,7 +65,7 @@ public class PhoneEncryptionConverter implements AttributeConverter<String, Stri
             cipher.init(Cipher.DECRYPT_MODE, secretKey, new GCMParameterSpec(GCM_TAG_LENGTH, iv));
             return new String(cipher.doFinal(ciphertext));
         } catch (Exception e) {
-            return encrypted;
+            throw new RuntimeException("Phone decryption failed", e);
         }
     }
 }