refactor: remove crudr peer transport

[raymondjacobson]

Summary

• remove CRUDR peer clients, push/sweep routes, upload scroller, outbox metrics, and seeding poller
• keep the local mediorum op-log/data-layer application path, with Core as the only metadata communication layer
• update tests that previously forced CRUDR sweeps to replay Core mediorum operations instead

Compatibility

• Backward compatible with the intended rollout stack: this should land only after PR1 readers and PR2 Core writers have shipped.
• Forward compatible: all metadata ops are carried by Core transactions, and repeated delivery remains idempotent by ULID.

Verification

• go test ./pkg/core/server -run 'Test(IsValidSignedTransaction|ValidateMediorumOperationShape)'
• go test ./pkg/mediorum/crudr -run '^$'
• go test -c ./pkg/mediorum/server -o /tmp/mediorum-server-pr3.test
• git diff --cached --check