chore: bump rust to 1.98

[0xForerunner]

Note

Low Risk
Toolchain bump plus mechanical test attributes and a no-op control-flow cleanup in constraint validation; no runtime behavior change intended.

Overview
Upgrades the repo from Rust 1.93.0 to 1.98.0 via rust-toolchain.toml.

To keep the tree green on the new compiler, integration and e2e test crates get #![recursion_limit = "256"] (core authenticator tests and gateway test modules) so deeply nested macro/type expansion still compiles.

In validate_max_nodes (constraints.rs), the All / Any / Enumerate arms no longer each end with true; control falls through to a single true after the match, with the same short-circuit behavior when count_node fails.

A stray blank line after the crate doc in services/common/src/lib.rs is removed.

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