feat(account): add eligible Intern picker query

src/main/java/com/lab/labtimesheet/feature/account/model/dto/EligibleInternOption.java

@@ -0,0 +1,21 @@
+package com.lab.labtimesheet.feature.account.model.dto;
+
+import java.time.LocalDate;
+
+/**
+ * Immutable non-secret selection data for an eligible Intern.
+ * The numeric user ID is the internal form submission identity; displayed fields are not authorization identifiers.
+ *
+ * @param userId persistent account identifier submitted by a consuming form
+ * @param displayName user-facing Intern name
+ * @param studentCode university student code shown to distinguish Interns
+ * @param internshipStart inclusive internship eligibility start date
+ * @param internshipEnd inclusive internship eligibility end date
+ */
+public record EligibleInternOption(
+        long userId,
+        String displayName,
+        String studentCode,
+        LocalDate internshipStart,
+        LocalDate internshipEnd) {
+}

src/main/java/com/lab/labtimesheet/feature/account/repository/InternProfileRepository.java

@@ -1,8 +1,12 @@
 package com.lab.labtimesheet.feature.account.repository;
 
 import java.time.LocalDate;
+import java.util.List;
 
+import com.lab.labtimesheet.feature.account.model.AccountStatus;
+import com.lab.labtimesheet.feature.account.model.GlobalRole;
 import com.lab.labtimesheet.feature.account.model.InternshipStatus;
+import com.lab.labtimesheet.feature.account.model.dto.EligibleInternOption;
 import com.lab.labtimesheet.feature.account.model.entity.InternProfile;
 import jakarta.persistence.LockModeType;
 import org.springframework.data.jpa.repository.JpaRepository;
@@ -19,6 +23,34 @@ public interface InternProfileRepository extends JpaRepository<InternProfile, Lo
     boolean existsByUserIdAndInternshipStatusAndInternshipStartDateLessThanEqualAndInternshipEndDateGreaterThanEqual(
             Long userId, InternshipStatus status, LocalDate latestStartDate, LocalDate earliestEndDate);
 
+    /**
+     * Projects account-owned non-secret selection data for Interns eligible on one inclusive business date.
+     * Results are ordered by display name, student code, then user ID for deterministic form rendering.
+     *
+     * @param globalRole required immutable Intern role
+     * @param accountStatus required active account state
+     * @param internshipStatus required active internship state
+     * @param businessDate date that must fall within the inclusive internship range
+     * @return eligible Intern selection projections without duplicate profile rows
+     */
+    @Query("""
+            select new com.lab.labtimesheet.feature.account.model.dto.EligibleInternOption(
+                u.id, u.displayName, p.studentCode, p.internshipStartDate, p.internshipEndDate)
+            from InternProfile p
+            join AppUser u on u.id = p.userId
+            where u.globalRole = :globalRole
+              and u.accountStatus = :accountStatus
+              and p.internshipStatus = :internshipStatus
+              and p.internshipStartDate <= :businessDate
+              and p.internshipEndDate >= :businessDate
+            order by u.displayName asc, p.studentCode asc, u.id asc
+            """)
+    List<EligibleInternOption> findEligibleInternOptions(
+            @Param("globalRole") GlobalRole globalRole,
+            @Param("accountStatus") AccountStatus accountStatus,
+            @Param("internshipStatus") InternshipStatus internshipStatus,
+            @Param("businessDate") LocalDate businessDate);
+
     /** Counts Intern profiles in a lifecycle state. */
     long countByInternshipStatus(InternshipStatus status);
 

src/main/java/com/lab/labtimesheet/feature/account/service/AccountService.java

@@ -8,6 +8,7 @@ import java.time.Clock;
 import java.time.Duration;
 import java.time.LocalDate;
 import java.util.Base64;
+import java.util.List;
 
 import com.lab.labtimesheet.feature.account.model.AccountStatus;
 import com.lab.labtimesheet.feature.account.model.GlobalRole;
@@ -17,6 +18,7 @@ import com.lab.labtimesheet.feature.account.model.dto.AccountCreation;
 import com.lab.labtimesheet.feature.account.model.dto.AccountIdentity;
 import com.lab.labtimesheet.feature.account.model.dto.AccountSummary;
 import com.lab.labtimesheet.feature.account.model.dto.CreateAccountCommand;
+import com.lab.labtimesheet.feature.account.model.dto.EligibleInternOption;
 import com.lab.labtimesheet.feature.account.model.entity.AppUser;
 import com.lab.labtimesheet.feature.account.model.entity.InternProfile;
 import com.lab.labtimesheet.feature.account.model.entity.UserActionToken;
@@ -238,6 +240,24 @@ public class AccountService {
                 .isPresent();
     }
 
+    /**
+     * Lists non-secret Intern selection options eligible on an explicit business date.
+     * The result requires active account and internship states plus inclusive internship dates, but it does not
+     * authorize a consuming Project operation; that operation must recheck its own ownership and membership rules.
+     *
+     * @param businessDate server-derived business date to evaluate inclusively
+     * @return deterministic options ordered by display name, student code, then account ID
+     * @throws IllegalArgumentException when {@code businessDate} is {@code null}
+     */
+    @Transactional(readOnly = true)
+    public List<EligibleInternOption> eligibleInternOptions(LocalDate businessDate) {
+        if (businessDate == null) {
+            throw new IllegalArgumentException("Business date is required");
+        }
+        return internProfiles.findEligibleInternOptions(
+                GlobalRole.INTERN, AccountStatus.ACTIVE, InternshipStatus.ACTIVE, businessDate);
+    }
+
     /**
      * Resolves the cross-feature identity of a currently eligible Intern.
      *