Use T3 remaining limit query

[decofe]

Summary

• query access-key spending limits through getRemainingLimitWithPeriod
• return the remaining field to preserve the existing query_key_spending_limit API

Context

Tempo T3 dropped the legacy getRemainingLimit selector. Callers using the old selector fail to read remaining limits.

Verification

• cargo test --manifest-path Cargo.toml client::tempo::signing::keychain --features tempo,client -q currently fails in tempo-contracts 1.7.0 with duplicate helper definitions generated by the Alloy sol macro; the selector change itself is a small ABI call replacement.
• A 0.9.3-compatible branch with the same one-line fix was used by Bump mpp for T3 remaining limit query wallet#464 and verified there with cargo check -p tempo-wallet --locked and focused whoami tests.

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