Manual Event Registration to Contract Macro

[moCello]

Summary

The macro extracts events by walking the AST of impl block methods looking for abi::emit() calls. This misses events emitted by:

1. Helper functions outside the impl block
2. Trait default implementations (e.g., OwnableUpgradeable::transfer_ownership emits OwnershipTransferred)

Possible Solution

Add an emits attribute to manually register events on trait impl blocks:

#[contract(expose = [owner, transfer_ownership, renounce_ownership],
           emits = [
               (events::OwnershipTransferred::OWNERSHIP_TRANSFERRED, events::OwnershipTransferred),
               (events::OwnershipTransferred::OWNERSHIP_RENOUNCED, events::OwnershipTransferred),
           ])]
impl OwnableUpgradeable for TestBridge { ... }

Each tuple is (topic_path, EventType) where topic can be a const path or string literal.