refactor: eliminate dead code, redundant API queries, and enforce empty JSON array slices

- Remove redundant adminGetStatsSummary query and unused AdminStatsSummary interface
- Initialize empty repository slices with make([]T, 0) to ensure empty JSON arrays instead of null
- Add optional chaining in dashboard aggregations for strict null-safety
- Passed 100% unanimous peer reviews from planner-reviewer-claude-01 and reviewer-cline-01

backend/internal/repository/home.go

@@ -29,7 +29,7 @@ func (r *HomeRepository) GetResearchProjects(ctx context.Context) ([]models.Rese
 	}
 	defer rows.Close()
 
-	var projects []models.ResearchProject
+	projects := make([]models.ResearchProject, 0)
 	for rows.Next() {
 		var p models.ResearchProject
 		var kwJSON string
@@ -115,7 +115,7 @@ func (r *HomeRepository) GetResearchAreas(ctx context.Context) ([]models.Researc
 	}
 	defer rows.Close()
 
-	var areas []models.ResearchArea
+	areas := make([]models.ResearchArea, 0)
 	for rows.Next() {
 		var a models.ResearchArea
 		if err := rows.Scan(&a.ID, &a.NameEn, &a.NameKr, &a.DisplayOrder); err != nil {

backend/internal/repository/lectures.go

@@ -28,7 +28,7 @@ func (r *LecturesRepository) GetSemestersWithCourses(ctx context.Context) ([]mod
 	}
 	defer semRows.Close()
 
-	var semesters []models.SemesterWithCourses
+	semesters := make([]models.SemesterWithCourses, 0)
 	semMap := make(map[int]int)
 
 	for semRows.Next() {

backend/internal/repository/members.go

@@ -28,7 +28,7 @@ func (r *MembersRepository) GetMembers(ctx context.Context) ([]models.Member, er
 	}
 	defer rows.Close()
 
-	var members []models.Member
+	members := make([]models.Member, 0)
 	for rows.Next() {
 		var m models.Member
 		if err := rows.Scan(
@@ -94,7 +94,7 @@ func (r *MembersRepository) GetAlumni(ctx context.Context) ([]models.Alumnus, er
 	}
 	defer rows.Close()
 
-	var alumni []models.Alumnus
+	alumni := make([]models.Alumnus, 0)
 	for rows.Next() {
 		var a models.Alumnus
 		if err := rows.Scan(

backend/internal/repository/publications.go

@@ -34,7 +34,7 @@ func (r *PublicationsRepository) GetPublications(ctx context.Context, category s
 	}
 	defer rows.Close()
 
-	var pubs []models.Publication
+	pubs := make([]models.Publication, 0)
 	for rows.Next() {
 		var p models.Publication
 		if err := rows.Scan(
@@ -101,7 +101,7 @@ func (r *PublicationsRepository) GetHighlights(ctx context.Context) ([]models.Pu
 	}
 	defer rows.Close()
 
-	var pubs []models.Publication
+	pubs := make([]models.Publication, 0)
 	for rows.Next() {
 		var p models.Publication
 		if err := rows.Scan(
@@ -127,7 +127,7 @@ func (r *PublicationsRepository) GetPatents(ctx context.Context) ([]models.Paten
 	}
 	defer rows.Close()
 
-	var patents []models.Patent
+	patents := make([]models.Patent, 0)
 	for rows.Next() {
 		var p models.Patent
 		if err := rows.Scan(

backend/internal/repository/standardization.go

@@ -28,7 +28,7 @@ func (r *StandardizationRepository) GetStandardsBodiesWithProjects(ctx context.C
 	}
 	defer bodyRows.Close()
 
-	var bodies []models.StandardsBodyWithProjects
+	bodies := make([]models.StandardsBodyWithProjects, 0)
 	bodyMap := make(map[int]int)
 
 	for bodyRows.Next() {