feat: Sync builder_files with page/script delete and rename operations

[asaura08]

Problem

When a page is marked as a standard page, Builder writes its source files to
{app}/builder_files/pages/{page_name}/. However, when that page (or any of its
client scripts) was deleted or renamed through the Builder UI or Desk, the
corresponding files on disk were not removed or updated. This left orphaned
directories in the app's source code that had no corresponding record in the
database — inconsistent with how Frappe handles standard DocTypes in developer
mode.

fix #496

Solution

Mirrors the behaviour of Frappe's own DocType sync in developer mode: any
filesystem artifact created when a record is exported must be cleaned up when
that record is deleted or renamed.

now

Changes

builder/export_import_standard_page.py

• delete_standard_page_files(page_name, app_name) — removes
  builder_files/pages/{export_name}/.
• delete_standard_client_script_files(script_name, app_name) — removes
  builder_files/client_scripts/{export_name}/.
• rename_standard_client_script_files(old, new, app_name) — renames the
  client-script directory and its inner JSON file.

builder/doctype/builder_page/builder_page.py

• on_trash — when is_standard, app and developer_mode are set, deletes
  the page directory and any client-script directories that are no longer
  referenced by another standard page in the same app.
• after_rename — deletes the old page directory; the subsequent on_update
  call re-exports the page under the new name automatically.

builder/doctype/builder_client_script/builder_client_script.py

• on_trash — removes the script's builder_files directory for every app
  whose standard pages reference it.
• after_rename — renames the script directory in every referencing app.
• _get_referencing_apps() — helper that returns the unique set of apps whose
  standard pages link to this script.

frontend/src/components/Settings/PageGeneral.vue

• Added a Page Name field (visible in developer mode when the page is
  standard) that allows renaming the exported file directly from the Builder UI,
  without having to go to Desk.
• The rename is committed on Enter or when the field loses focus (focusout).

builder/doctype/builder_page/builder_page.js

• Fixed a bug where the installed-apps list was being assigned to the wrong
  field (module instead of app), which caused the App select in the
  Desk form to appear empty.

frontend/src/components/PageActionsDropdown.vue

• The Delete action is now shown for standard pages when developer_mode is
  active, consistent with the rest of the developer-mode affordances.

Tests

TestStandardPageSync (6 cases) covers:

1. on_trash removes the page directory.
2. on_trash removes an orphaned client-script directory.
3. on_trash does not remove a client-script directory shared by another
   standard page.
4. after_rename deletes the old directory and re-exports under the new name.
5. Client-script on_trash removes the script's directory.
6. Client-script after_rename renames the directory and inner JSON file.

[stravo1]

Hi, thanks for the PR!

I noticed a couple of things that could be improved.

It works correctly when directly deleting a standard page (more on this below*), but if I first uncheck “Standard Page”, the files remain. Then, when deleting that now non-standard page, the files are still not removed, since on_trash checks the is_standard property, which is now false.

*In the PR, deleting a standard page is allowed in Developer Mode. However, I feel it might be better to keep the “Delete” action in PageActionsDropdown.vue hidden for standard pages, even in Developer Mode.

Perhaps a cleaner approach would be to delete the page files when the “Standard Page” toggle is unchecked. This seems like a better UX and would also remove the need to enable the “Delete” action in Developer Mode.

@asaura08 @surajshetty3416