NetworkBanner/NetworkScreen fixes for #170

[frankrichard99]

Summary

Issue #170 reported three problems in NetworkBanner and NetworkScreen:

1. The banner rendered redundantly on the Network screen itself
2. InfoCell values (passphrase, RPC URL, Horizon URL) had no copy mechanism
3. The banner had no transition animation on network switch

All three fixes were already implemented and merged to main in commits
cddfe68, 3b9b7c5, and d7064cd, but the change was never recorded in
CHANGELOG.md and the issue was left open without a closing reference.

This PR closes that gap by adding a ### Fixed entry under [Unreleased]
documenting the change, and closes the issue.

Changes

• MODIFIED CHANGELOG.md
  • Added a ### Fixed subsection under ## [Unreleased] documenting:
    • NetworkBanner suppression on the Network screen
    • Copy-to-clipboard buttons on Passphrase / RPC URL / Horizon URL InfoCells
    • Smooth transition-all duration-300 fade on NetworkBanner network switch

Verification

• Confirmed via git diff main -- src/components/NetworkBanner.tsx src/screens/NetworkScreen.tsx that all three fixes already exist on main:
  • NetworkBanner.tsx: if (active === "network") return null; and transition-all duration-300 on the root div
  • NetworkScreen.tsx: copyable prop wired to Passphrase, RPC URL, and Horizon URL InfoCells, using the same copy-icon pattern as AddressDisplay
• npm run build passes
• This is a documentation-only change; no source/test files were modified

Closes #170