refactor: export SanitizeTail and DefaultLogTail directly instead of wrapping

- Rename sanitizeTail → SanitizeTail (exported)
- Rename defaultLogTail → DefaultLogTail (exported)
- Delete export_test.go (no longer needed)
- Update test to reference handlers.SanitizeTail/DefaultLogTail directly

internal/handlers/app.go

@@ -382,22 +382,22 @@ func (h *Handlers) HandleAppDeployments() http.HandlerFunc {
 	}
 }
 
-// defaultLogTail is the default number of log lines to fetch.
-const defaultLogTail = "500"
+// DefaultLogTail is the default number of log lines to fetch.
+const DefaultLogTail = "500"
 
 // maxLogTail is the maximum allowed value for the tail parameter.
 const maxLogTail = 500
 
-// sanitizeTail validates and clamps the tail query parameter.
+// SanitizeTail validates and clamps the tail query parameter.
 // It returns a numeric string clamped to maxLogTail, or the default if invalid.
-func sanitizeTail(raw string) string {
+func SanitizeTail(raw string) string {
 	if raw == "" {
-		return defaultLogTail
+		return DefaultLogTail
 	}
 
 	n, err := strconv.Atoi(raw)
 	if err != nil || n < 1 {
-		return defaultLogTail
+		return DefaultLogTail
 	}
 
 	if n > maxLogTail {
@@ -428,7 +428,7 @@ func (h *Handlers) HandleAppLogs() http.HandlerFunc {
 			return
 		}
 
-		tail := sanitizeTail(request.URL.Query().Get("tail"))
+		tail := SanitizeTail(request.URL.Query().Get("tail"))
 
 		logs, logsErr := h.docker.ContainerLogs(
 			request.Context(),