feat(stellar/wraith-names): sealed-bid auctions for premium names

[raizo07]

closes #117

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[truthixify]

Full CI never ran on this branch since it predates the CI-trigger fix on develop. Rebase against latest develop and force-push to get the signal.

[truthixify]

The stellar job fails at cargo test --workspace with:

• error[E0432]: unresolved import wraith_names::AuctionError
• error[E0599]: no method named init_auctions found for WraithNamesContractClient
• error[E0599]: no method named start_auction found for WraithNamesContractClient

Your auction module is not wired into the contract's public API. Fix: in wraith-names/src/lib.rs add pub mod auction; and re-export the types, then add the init_auctions / start_auction methods to the #[contractimpl] impl WraithNamesContract block so the generated client picks them up. The tests can't see private/module-scoped items.