refactor(lints): adopt #[expect] and fix crypto/frost lint inheritance

[varex83agent]

Closes #609.

Converted ~76 justified #[allow]/#![allow] suppressions in hand-written code to #[expect(..., reason = "...")] (0 -> 84 #[expect] attrs; non-generated bare #[allow] count dropped from ~92 to 16, each now carrying a reason). Removed several stale suppressions whose wiring has landed (e.g. dead_code on tracker/inclusion.rs, tracker/reason.rs, validatorapi fields, dkg signing, and a now-transformed too_many_arguments on BeaconMock::new). Cases where #[expect] would be unfulfilled on some target (e.g. async_fn_in_trait, test/example missing_docs, deprecated, test-only dead_code) are kept as #[allow] with an explanatory reason comment. Generated code (proto includes, build-proto, eth2api bindings) and tbls::math's unsafe_code opt-in were left untouched.

Fixed the crypto/frost [lints] inheritance drift: both re-listed the clippy set by hand and missed the workspace-denied redundant_test_prefix. Cargo does not allow [lints] workspace = true combined with a per-lint override, and both crates must relax unsafe_code for the blst C bindings, so the lint set is now listed explicitly, completed with redundant_test_prefix, and documented as needing to stay in sync with [workspace.lints].

Gates: cargo +nightly fmt --all --check, cargo clippy --workspace --all-targets --all-features -- -D warnings, and cargo test --workspace --all-features all pass.

Co-Authored-By: Bohdan Ohorodnii 35969035+varex83@users.noreply.github.com