Release 1.13.0

This is a feature release for Vouch. Highlights include:

• add combinedmajority attestationdata strategy
• update go-eth2-wallet-dirk to v1.6.0
• update go-eth2-client to v0.28.0
• update go version to 1.25.5
• cancel open http requests when strategies.builderbid.best.timeout is reached
• fix sync committee signing when a validator occupies multiple positions
• use block headers as primary fetch in cache handleHead; full blocks are best-effort
• migrate Dirk and tracing TLS certificate loading to go-certmanager
• remove dead priorBlocksVotes cache from beaconblockproposal/best strategy
• downgrade warn level log messages to debug for timeouts and provider failures on first strategies