fix: allow A-Z, underscore, and dash in SanitizeFilename

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: AchoArnold

api/pkg/repositories/attachment_repository.go

@@ -83,8 +83,8 @@ func SanitizeFilename(name string, index int) string {
 	name = strings.TrimSuffix(name, filepath.Ext(name))
 
 	var builder strings.Builder
-	for _, r := range strings.ToLower(name) {
-		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
+	for _, r := range name {
+		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '_' || r == '-' {
 			builder.WriteRune(r)
 		} else if r == ' ' {
 			builder.WriteRune('-')

api/pkg/repositories/attachment_repository_test.go

@@ -43,13 +43,13 @@ func TestSanitizeFilename(t *testing.T) {
 		{"photo.jpg", 0, "photo"},
 		{"../../etc/passwd", 0, "etcpasswd"},
 		{"hello/world\\test", 0, "helloworldtest"},
-		{"normal_file", 0, "normalfile"},
+		{"normal_file", 0, "normal_file"},
 		{"", 0, "attachment-0"},
 		{"   ", 0, "attachment-0"},
 		{"...", 1, "attachment-1"},
-		{"My Photo", 0, "my-photo"},
+		{"My Photo", 0, "My-Photo"},
 		{"file name with spaces.png", 0, "file-name-with-spaces"},
-		{"UPPER_CASE", 0, "uppercase"},
+		{"UPPER_CASE", 0, "UPPER_CASE"},
 		{"special!@#chars", 0, "specialchars"},
 	}
 	for _, tt := range tests {