Add PageNoteButton to various components for enhanced note management

WebApp/Services/MarkdownHelper.cs

@@ -92,4 +92,16 @@ public static class MarkdownHelper
 
         return plainText;
     }
+
+    /// <summary>
+    /// Gets the CSS class name for a note's color based on its ID.
+    /// Uses modulo 3 to cycle through 3 pastel color classes.
+    /// </summary>
+    /// <param name="noteId">The note ID.</param>
+    /// <returns>CSS class name (e.g., "note-color-0", "note-color-1", "note-color-2"), or empty string if noteId is 0.</returns>
+    public static string GetNoteColorClass(int noteId)
+    {
+        if (noteId == 0) return string.Empty;
+        return $"note-color-{noteId % 3}";
+    }
 }