[user_accounts] Reactify the edit user page

[Montekkundan]

Brief summary of changes

• Replaces the Smarty edit-user template with a TypeScript React form.
• Preserves the existing PHP form submission, validation, permission, supervisor, and account-rejection behavior.
• Preserves password generation, username matching, Reset, Back, Save, and self-edit restrictions.
• Keeps permission controls mounted when their groups are collapsed so selected permissions remain part of form submissions.
• Adds the user_accounts webpack entry and Makefile build target.
• Removes the retired Smarty template and its legacy JavaScript helpers.
• Keeps generated JavaScript bundles and source maps ignored.

Testing instructions

• Open http://localhost:8080/user_accounts/edit_user/.
• Confirm the create-user form loads with the existing fields and field order.
• Test matching the username to the email address and generating a password.
• Create a user and confirm the existing backend validation and success behavior.
• Edit an existing user and confirm sites, projects, permissions, and supervisors save correctly.
• Collapse a permission group before saving and confirm its selected permissions are preserved.
• Open your own account and confirm all editable controls and the Save button are disabled.
• Run make user_accounts.

Link(s) to related issue(s)

• Resolves [user_accounts] Reactify the edit user page #10819