p2p: make safety limits configurable (caps + per-peer budgets + relay cache bounds)

[TheNewAutonomy]

Goal

Make P2P safety limits tunable per network (dev/testnet/mainnet) without code changes, while keeping strict validation and safe defaults.

Context

We implemented conservative hard defaults for:

• libp2p gossipsub message caps + per-peer budgets (crates/catalyst-network/src/service.rs)
• simple TCP frame caps + per-connection budgets (crates/catalyst-network/src/simple.rs)
• relay dedup cache bounding (RelayCache in crates/catalyst-cli/src/node.rs)

This ticket is to move those knobs into config and validate them.

Scope

• Add config fields (with safe defaults) for:
  • max gossip message bytes
  • per-peer msgs/sec and bytes/sec
  • max TCP frame bytes
  • per-connection msgs/sec and bytes/sec
  • relay cache max/target size and retention window
• Validate bounds on startup (refuse unsafe/unbounded values).
• Document recommended defaults for public testnet vs mainnet.

Acceptance criteria

• Operators can tune limits in config.toml.
• Nodes enforce configured limits deterministically.
• Invalid configs are rejected with actionable errors.

[TheNewAutonomy]

Implemented configurable P2P safety limits + relay cache bounds (config.toml-driven):

New node config keys

Under [network]:

• safety_limits.*:
  • max_gossip_message_bytes
  • per_peer_max_msgs_per_sec
  • per_peer_max_bytes_per_sec
  • max_tcp_frame_bytes
  • per_conn_max_msgs_per_sec
  • per_conn_max_bytes_per_sec
  • max_hops
  • dedup_cache_max_entries
  • dial_jitter_max_ms
  • dial_backoff_max_ms
• relay_cache.*:
  • max_entries
  • target_entries
  • retention_seconds

Wiring/enforcement

• catalyst-network:
  • Added NetworkConfig.safety_limits with safe defaults + validation.
  • libp2p transport enforces caps/budgets using configured values.
  • simple TCP transport enforces frame cap, per-conn budgets, multi-hop hop limit, and dedup cache bound.
• catalyst-cli:
  • Node config now exposes network.safety_limits and network.relay_cache (with validation).
  • Node maps these into the P2P config and RelayCache at startup.

Defaults match the previous hard-coded values (8MiB caps, 200 msgs/sec, 8MiB/sec, max_hops=10, jitter<=250ms, backoff cap=60s; relay cache max=5000/target=4000/retain=600s).

Remaining follow-up for this ticket (if desired):

• Document recommended testnet vs mainnet settings in operator docs.