fix(anvil): guard zero prune history limit

[mk0walsk]

Motivation

Passing --prune-history 0 can propagate a zero max_memory_history into InMemoryBlockStates, where enforce_limits loops on while self.present.len() >= self.in_memory_limit. With a zero limit, that condition never becomes false, which can leave Anvil stuck while pruning state history.

Solution

Treat 0 as an unsupported prune-history value at the config layer, and clamp in-memory cache limits to at least 1 in storage as a defensive fallback. This prevents the infinite eviction loop and adds regression tests for zero-value config parsing and cache initialization.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes