chore: add #[must_use] to constructors and accessor methods

[refcell]

Summary

• Adds #[must_use] annotations to all public constructors and accessor methods across the codebase
• Improves code quality by catching accidental non-usage of important return values
• Ensures consistency with Rust idioms for builder and factory patterns

Changes

• IndexedStateProvider::new in crates/node/rpc/src/indexed_provider.rs
• RevmExecutor::new and RevmExecutor::with_config in crates/node/executor/src/revm.rs
• StateDbAdapter::new and StateDbAdapter::state in crates/node/executor/src/adapter.rs
• CommonwareRootProvider::new and all accessor methods in crates/storage/backend/src/backend.rs
• DkgCeremony::new and DkgCeremony::new_with_force_restart in crates/node/dkg/src/ceremony.rs
• Tx::new in crates/node/domain/src/tx.rs
• BootstrapConfig::new in crates/node/domain/src/bootstrap.rs
• BlockContext::new in crates/node/executor/src/context.rs
• KoraApiImpl::new in crates/node/rpc/src/kora.rs
• StorageKey::new in crates/storage/qmdb/src/encoding.rs

Verification

• ✅ cargo clippy --all-targets --all-features -- -D warnings passes
• ✅ cargo nextest run --workspace --all-features passes (498 tests)
• ✅ No breaking changes to public APIs