Add Token SAC review re-fetches fee + scan data the Add Token screen already loaded

[piyalbasu]

Summary

In the Add Token → SAC trustline review flow, ChangeTrustInternal re-fetches
data that the Add Token screen already loaded, adding avoidable latency and
duplicate backend requests. Not user-visible beyond the extra round-trips.
Follow-up from the PR #2869 review (finding #6, [efficiency]).

Details

extension/src/popup/components/manageAssets/ManageAssetRows/ChangeTrustInternal/index.tsx

• Duplicate feeStats() round-trip. ChangeTrustInternal calls
  useNetworkFees() again even though the Add Token screen already fetched fees.
  Only initialFee is threaded down from the parent — not recommendedFee — so
  the child re-fetches to recover it.
• Duplicate scanAsset. useChangeTrustData re-runs scanAsset for the
  same ${code}-${issuer} the Add Token screen already scanned; the prior scan
  result is not threaded down.

Proposed fix

Thread the already-fetched recommendedFee and the Add Token scan result down
into ChangeTrustInternal (via props) instead of re-fetching them in the child.

Related note to verify (not necessarily blocking)

fetchData is useCallback-memoized with networkDetails in its dep array and
the effect depends on [fetchData]. This is correct only while the
networkDetails prop is referentially stable. If a parent ever passes a
freshly-constructed networkDetails each render, the memo breaks and fetchData
re-fires every render. Current tests pass, so the useGetAppData/redux source
appears stable — worth a quick confirmation while in this code.

Context

• Source: local PR review of Improve Add Token disclosure for SAC #2869 (feat/addtoken-sac-changetrust-review), head b314de9b.
• Severity: low (latency / duplicate requests only; no correctness or security impact).