Fix security vulnerabilities, fix MSRV, migrate structopt to clap v4

[ma2bd]

Summary

• Migrate serde-generate-bin from structopt (which depends on clap v2 and atty) to clap v4 with derive, removing the atty vulnerability (GHSA Upgrade Rust Toolchain to 1.60 #4)
• Update transitive dev-dependencies: keccak 0.1.5 to 0.1.6 (GHSA Fix copyright with Ocaml-related files #8), bytes 1.9.0 to 1.11.1 (GHSA Dart utf8 #6)
• Bump rust-version for serde-generate-bin from 1.70 to 1.88
• Downgrade MSRV to 1.82 with a comment related to the feature solidity
• Remove solidity and typescript from the default features

Addresses all 4 open Dependabot alerts:

Alert	Package	Severity	Fix
#8	keccak	Low	cargo update
#7	tracing-subscriber	Low	Already resolved
#6	bytes	Medium	cargo update
#4	atty	Low	Replaced structopt with clap v4

Test plan

• cargo clippy --locked --workspace --all-features --all-targets passes clean
• cargo test --locked --no-default-features --no-run passes clean
• serdegen --help works correctly with clap v4
• atty and structopt no longer appear in cargo tree

🤖 Generated with Claude Code