fix(ux): show unsaved changes warning on cancel in route and upstream…

[vanshaj2023]

Why submit this pull request?

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What changes will this PR take into?

When editing a Route or Upstream and clicking Cancel, all unsaved form changes were silently discarded with no warning. This PR adds a confirmation dialog (same pattern as #3333) that appears only when the form has unsaved changes.

• Added handleCancel in routes/detail.$id.tsx and upstreams/detail.$id.tsx that checks form.formState.isDirty before closing
• If dirty → shows "Unsaved Changes" confirmation modal with Discard/Cancel options
• If clean → closes silently without modal
• Added info.unsaved.* i18n keys across all 5 locales (en, zh, de, es, tr)

Note: form.formState.isDirty is reliable here because form.reset(fetchedData) is called after data loads, correctly setting defaultValues. This is different from #3333 where direct value comparison was needed.

Related issues

fix #3344

Checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[vanshaj2023]

Hi @Baoyuantop ,
Please review this.