Add hyperlink to "Application Number" field in Budget Filing

Update the "Application Number" field in budget filing advice letters to allow entry of a clickable URL. The field should remain optional and editable, but must validate that the input is a properly formatted URL (starting with http:// or https://).

Questions:

1. Do we want to ask for an application number and an advice letter for 2026⁄2027?
   Yes, MCAL will have both

2. Do we want to ask for application number and an advice letter for the filings after 2026⁄2027?
   Yes, but they should not be required

3. Should these field be required at the initiation step 1?
   URLs are not required at initiation.

4. What symbols should be allowed for these fields currently cedars is allowing - and _?
   We need slashes too