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

### 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:

```ts
setReadOnly(true)}>
{t('form.btn.cancel')}

```

### 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`)

Start by reading upstreams/detail.$id.tsx and routes/detail.$id.tsx, then compare their Cancel handling with the plugin editor drawer changes in #3333. Reproduce the edit-and-cancel flow on both affected pages and verify that a confirmation appears only when changes are unsaved and that confirmed cancellation discards them.

Written by the indexing model from the issue text.