Feature/v2/add text (#4951)

Refactor sign to separate out add text and add image functions. 
Implement add text as standalone tool

frontend/src/core/tools/AddText.tsx

@@ -0,0 +1,12 @@
+import { createStampTool } from '@app/tools/stamp/createStampTool';
+
+// AddText is text-only annotation (no drawing, no images, no save-to-library)
+const AddText = createStampTool({
+  toolId: 'addText',
+  translationScope: 'addText',
+  allowedSignatureSources: ['text'],
+  defaultSignatureSource: 'text',
+  defaultSignatureType: 'text',
+});
+
+export default AddText;