feat(core): real-time escrow event subscription (SSE + reconnection)

[aguilar1x]

Context

The widget and integrators need to react to the real escrow lifecycle in real time.

Scope

• session.on('escrow.funded' | 'fiat.reported' | 'released' | 'disputed', cb) over SSE/WebSocket.
• Automatic reconnection with cursor-based replay of missed events + heartbeat.
• Event names must reflect the real escrow_milestones states in Pacto P2P.

Acceptance criteria

• After a network drop it reconnects without losing events.
• Events map to real escrow lifecycle states (funded → fiat reported → released / disputed).

Dependencies

#12 and #13.

[diegocintron]

Hello,

I'd like to take this issue.

I enjoy working on challenging problems and contributing to open-source projects. I've reviewed the requirements and would be happy to work on a solution if assigned.

Looking forward to contributing.

[grantfox-oss]

🦊 GrantFox — @diegocintron has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #14)
2. Your PR will be reviewed by the PACTO-LAT maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@diegocintron's PR #24 was approved and merged by @aguilar1x.

🏆 @diegocintron: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (48 total points). Track your full progress on GrantFox.

👏 Great work, @diegocintron! Keep contributing to PACTO-LAT.