chore: bump salt version to 1.0.3

[flyq]

Summary

• Bump salt crate version from 1.0.2 to 1.0.3 in salt/Cargo.toml and Cargo.lock
• Prepares a patch release covering the changes landed on main since v1.0.2

Changes since v1.0.2

• salt: plain_value_and_slot accessor + drop hashbrown/serde feature (salt: plain_value_and_slot accessor + drop hashbrown/serde feature #131)
  • Adds PlainStateProvider::plain_value_and_slot so callers that need the SlotId (or the encoded record) can skip plain_value's Vec<u8> copy.
  • Drops the hashbrown/serde feature flag and hand-writes Serialize/Deserialize for SaltProof::levels, unblocking downstream alloy-tx-macros 1.0.23 which couldn't compile against the transitively-bumped serde_core ≥ 1.0.221.

Only the salt crate is bumped; banderwagon, ipa-multipoint, and salt-macros remain at 0.1.0 as internal path-dependencies with no public release cadence.

Test plan

• cargo build --workspace succeeds
• cargo test --workspace passes
• cargo build -p salt --no-default-features (verify no_std path still green)

[github-actions]

Performance Benchmark Comparison

Compared 5 benchmark(s) against the latest main baseline.

Detailed Comparison

Benchmark	Baseline Throughput (Kelem/s)	New Throughput (Kelem/s)	Change
update 10000 KVs/1 threads	43.78	43.04	-1.71%
update 10000 KVs/2 threads	81.85	81.17	-0.83%
update 10000 KVs/4 threads	150.79	149.37	-0.94%
update 10000 KVs/8 threads	267.13	263.63	-1.31%
update 10000 KVs/16 threads	391.85	394.61	+0.70%