feat: Add UI to manage web widget allowed domains (#12495)

## Summary
- add allowed domains controls in the web widget configuration page.

<img width="1064" height="699" alt="Screenshot 2025-09-23 at 8 52 21 PM"
src="https://github.com/user-attachments/assets/8afd60b6-c81d-4f52-9cbe-07e70ad003d2"
/>


fixes:
https://linear.app/chatwoot/issue/CW-5661/add-the-options-for-configure-allowed-domains-for-web-widget

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/dashboard/helper/specs/URLHelper.spec.js

@@ -8,6 +8,7 @@ import {
   timeStampAppendedURL,
   getHostNameFromURL,
   extractFilenameFromUrl,
+  sanitizeAllowedDomains,
 } from '../URLHelper';
 
 describe('#URL Helpers', () => {
@@ -318,4 +319,32 @@ describe('#URL Helpers', () => {
       ).toBe('file.doc');
     });
   });
+
+  describe('sanitizeAllowedDomains', () => {
+    it('returns empty string for falsy input', () => {
+      expect(sanitizeAllowedDomains('')).toBe('');
+      expect(sanitizeAllowedDomains(null)).toBe('');
+      expect(sanitizeAllowedDomains(undefined)).toBe('');
+    });
+
+    it('trims whitespace and converts newlines to commas', () => {
+      const input = '  example.com  \n  foo.bar\nbar.baz  ';
+      expect(sanitizeAllowedDomains(input)).toBe('example.com,foo.bar,bar.baz');
+    });
+
+    it('handles Windows newlines and mixed spacing', () => {
+      const input = ' example.com\r\n\tfoo.bar  ,  bar.baz ';
+      expect(sanitizeAllowedDomains(input)).toBe('example.com,foo.bar,bar.baz');
+    });
+
+    it('removes empty values from repeated commas', () => {
+      const input = ',,example.com,,foo.bar,,';
+      expect(sanitizeAllowedDomains(input)).toBe('example.com,foo.bar');
+    });
+
+    it('lowercases entries and de-duplicates preserving order', () => {
+      const input = 'Example.com,FOO.bar,example.com,Bar.Baz,foo.BAR';
+      expect(sanitizeAllowedDomains(input)).toBe('example.com,foo.bar,bar.baz');
+    });
+  });
 });