Fix account name persistence source

[yvette-carlisle]

Summary

• restore the stable account alias candidate list so existing persisted offsets do not drift
• stop reading or writing dashboard account-name offsets from browser localStorage
• keep dashboard reroll state in-memory only while /api/accounts/reroll-name writes the global Decodex config

Verification

• cargo test -p decodex account
• cargo +nightly fmt --all -- --check
• swift build --package-path apps/decodex-app
• git diff --check
• sanitized decodex account list --json showed the shared account pool currently resolves to Mason / Iris / Avery, with no Alex
• Browser smoke: with stale local accountNameOffsets preloaded, hiding emails still rendered the server/global name Mason in the account table and run card