fix(ux): no unsaved changes warning when canceling edit on detail pages

[vanshaj2023]

Issue description

On detail/edit pages (Upstreams, Routes, Services, etc.), clicking Cancel silently discards all unsaved form changes with no warning. Users can lose edits without realizing it.

Root cause
The Cancel button calls setReadOnly(true) directly with no unsaved changes check:

<Button variant="outline" onClick={() => setReadOnly(true)}>
  {t('form.btn.cancel')}
</Button>

Expected behavior

A confirmation dialog should appear when the user has unsaved changes, consistent with the plugin editor drawer which was fixed in #3333 .

How to Reproduce

1. Go to Upstreams → open any upstream → click Edit
2. Make changes to any field
3. Click Cancel
4. All changes are silently discarded, no confirmation dialog

Screenshots

No response

Environment

apisix-dashboard: master

Additional context

Affected pages

1. Upstreams (upstreams/detail.$id.tsx)
2. Routes (routes/detail.$id.tsx)

[vanshaj2023]

Hi @Baoyuantop ,
I noticed the same issue that we fixed in #3333
Do I do the same thing here.