[autofix.ci] apply automated fixes

Bumps [docker/login-action](https://github.com/docker/login-action) from 3 to 4.
- [Release notes](https://github.com/docker/login-action/releases)
- [Commits](https://github.com/docker/login-action/compare/v3...v4)

---
updated-dependencies:
- dependency-name: docker/login-action
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -375,13 +375,13 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Login to Docker Hub
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Log in to GitHub Container Registry
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.actor }}

.github/workflows/release.yml

@@ -91,13 +91,13 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Login to Docker Hub
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Log in to GitHub Container Registry
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.actor }}

internal/exporters/markdown.go

@@ -40,19 +40,19 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	var buf bytes.Buffer
 
 	// Write course header
-	buf.WriteString(fmt.Sprintf("# %s\n\n", course.Course.Title))
+	fmt.Fprintf(&buf, "# %s\n\n", course.Course.Title)
 
 	if course.Course.Description != "" {
-		buf.WriteString(fmt.Sprintf("%s\n\n", e.htmlCleaner.CleanHTML(course.Course.Description)))
+		fmt.Fprintf(&buf, "%s\n\n", e.htmlCleaner.CleanHTML(course.Course.Description))
 	}
 
 	// Add metadata
 	buf.WriteString("## Course Information\n\n")
-	buf.WriteString(fmt.Sprintf("- **Course ID**: %s\n", course.Course.ID))
-	buf.WriteString(fmt.Sprintf("- **Share ID**: %s\n", course.ShareID))
-	buf.WriteString(fmt.Sprintf("- **Navigation Mode**: %s\n", course.Course.NavigationMode))
+	fmt.Fprintf(&buf, "- **Course ID**: %s\n", course.Course.ID)
+	fmt.Fprintf(&buf, "- **Share ID**: %s\n", course.ShareID)
+	fmt.Fprintf(&buf, "- **Navigation Mode**: %s\n", course.Course.NavigationMode)
 	if course.Course.ExportSettings != nil {
-		buf.WriteString(fmt.Sprintf("- **Export Format**: %s\n", course.Course.ExportSettings.Format))
+		fmt.Fprintf(&buf, "- **Export Format**: %s\n", course.Course.ExportSettings.Format)
 	}
 	buf.WriteString("\n---\n\n")
 
@@ -60,15 +60,15 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	lessonCounter := 0
 	for _, lesson := range course.Course.Lessons {
 		if lesson.Type == "section" {
-			buf.WriteString(fmt.Sprintf("# %s\n\n", lesson.Title))
+			fmt.Fprintf(&buf, "# %s\n\n", lesson.Title)
 			continue
 		}
 
 		lessonCounter++
-		buf.WriteString(fmt.Sprintf("## Lesson %d: %s\n\n", lessonCounter, lesson.Title))
+		fmt.Fprintf(&buf, "## Lesson %d: %s\n\n", lessonCounter, lesson.Title)
 
 		if lesson.Description != "" {
-			buf.WriteString(fmt.Sprintf("%s\n\n", e.htmlCleaner.CleanHTML(lesson.Description)))
+			fmt.Fprintf(&buf, "%s\n\n", e.htmlCleaner.CleanHTML(lesson.Description))
 		}
 
 		// Process lesson items