Idea Summary
Add the ability to define a custom name for the exported application file, both from the App Builder UI and from SQLcl.

Use Case
Currently, APEX exports are always named using a fixed convention (`f[APP_ID].sql` for classic exports, `[app-alias].zip` for APEXlang exports). This makes it difficult to:
- Identify exports at a glance when managing multiple versions or environments.
- Integrate exports into CI/CD pipelines that require meaningful, consistent file naming conventions.
- Include contextual information such as the application name, version, or export date directly in the filename, without relying on external shell scripts or manual renaming steps.

Preferred Solution
Add an optional *Export Filename* field in the export dialog (App Builder UI) that accepts static text and substitution strings such as `&APP_NAME.`, `&APP_ALIAS.`, or `&SYSDATE.`.

For example, a value like `&APP_ALIAS._&SYSDATE.` would produce a file named `my_app_20260529.sql` (or `.zip` for APEXlang exports).

The same capability should be available as a parameter in the `apex export` SQLcl command, for example:
`apex export -applicationid 100 -filename &APP_ALIAS._&SYSDATE.`

If no custom name is provided, the current default behavior (`f[APP_ID].sql` / `[app-alias].zip`) should be preserved for backward compatibility.