Avoid duplicate cached redirect headers

[Austin1serb]

Summary*

Fix duplicate headers when a cached App Router redirect response is replayed.
Applies to routes using dynamic = 'force-static' with redirect() or permanentRedirect().

Root cause

Cached response headers were appended directly to the native Node response. This bypassed the duplicate-value protection already implemented by NodeNextResponse.appendHeader.
As a result, headers such as Location and x-nextjs-stale-time could appear twice.

Changes

• Wrap the native response in NodeNextResponse.
• Replay cached headers through its appendHeader method.
• Identical values are no longer duplicated.
• Distinct values for legitimate multi-value headers remain supported.

Regression test

• Added a production App Router fixture with:

A catch-all route
dynamic = 'force-static'
permanentRedirect('/destination')
Inspected raw response headers.

• Confirmed there is exactly one Location value and one x-nextjs-stale-time value.

Validation

• Webpack production test passed.
• Turbopack production test passed.
• Next.js package build passed.
• ESLint passed.
• Prettier passed.

Fixes #82117