fix: resolve all golangci-lint errors and integrate linter into CI/CD, Makefile, and check script

internal/db/db.go

@@ -186,7 +186,9 @@ func (d *DB) ListCategories() ([]models.Category, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() {
+		_ = rows.Close()
+	}()
 
 	var categories []models.Category
 	for rows.Next() {
@@ -264,7 +266,9 @@ func (d *DB) ListFeeds() ([]models.Feed, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() {
+		_ = rows.Close()
+	}()
 
 	var feeds []models.Feed
 	for rows.Next() {
@@ -479,7 +483,9 @@ func (d *DB) UpsertFeedEntries(feedID string, entries []models.FeedEntry) (int,
 	if err != nil {
 		return 0, err
 	}
-	defer stmt.Close()
+	defer func() {
+		_ = stmt.Close()
+	}()
 
 	insertedCount := 0
 	for _, e := range entries {
@@ -519,9 +525,10 @@ func (d *DB) ListEntries(f EntryFilter) ([]models.FeedEntry, int, error) {
 	where := []string{"1=1"}
 	args := []interface{}{}
 
-	if f.View == "inbox" {
+	switch f.View {
+	case "inbox":
 		where = append(where, "e.is_read = 0")
-	} else if f.View == "starred" {
+	case "starred":
 		where = append(where, "e.is_starred = 1")
 	}
 
@@ -596,7 +603,9 @@ func (d *DB) ListEntries(f EntryFilter) ([]models.FeedEntry, int, error) {
 	if err != nil {
 		return nil, 0, err
 	}
-	defer rows.Close()
+	defer func() {
+		_ = rows.Close()
+	}()
 
 	var entries []models.FeedEntry
 	for rows.Next() {

internal/db/db_test.go

@@ -14,14 +14,18 @@ func TestDatabaseOperations(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to create temp dir: %v", err)
 	}
-	defer os.RemoveAll(tempDir)
+	defer func() {
+		_ = os.RemoveAll(tempDir)
+	}()
 
 	dbPath := filepath.Join(tempDir, "test.db")
 	database, err := InitDB(dbPath)
 	if err != nil {
 		t.Fatalf("InitDB failed: %v", err)
 	}
-	defer database.Close()
+	defer func() {
+		_ = database.Close()
+	}()
 
 	// 1. Test User
 	u, err := database.CreateUser("admin", "$2a$10$dummyhashvalue")