feat(protocols): implement protocol health monitoring

[feyishola]

closes #152

Protocol Health Monitoring — Implemented

Location: src/modules/protocols/health/

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Files Created

File	Purpose
interfaces/protocol-health.interface.ts	All types: ProtocolStatus, MetricType, MetricThreshold, DTOs, ProtocolAlert, ProtocolHealthSnapshot
protocol-health.service.ts	Core logic: metric collection, threshold evaluation, alert lifecycle
protocol-health.controller.ts	REST endpoints
protocol-health.module.ts	NestJS module
protocol-health.service.spec.ts	19 tests covering all scenarios

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REST API (/api/protocols/health)

Method	Path	Description
POST	/register	Register a protocol with metric thresholds
POST	/metrics	Record metric observations for a protocol
GET	/	Get all protocol health snapshots
GET	/alerts	Get all active (unresolved) alerts
GET	/:protocolId	Get a single protocol health snapshot

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How It Works

1. Register a protocol with per‑metric thresholds
   Example: warn when error_rate > 5%, critical when error_rate > 10%; or warn when transaction_count < 10.
   Supports four metric types:

   • transaction_count
   • error_rate
   • response_time_ms
   • active_users

2. Record metrics → triggers threshold checks

   • When a breach is detected → an alert is generated
   • When the metric recovers → the alert is auto‑resolved
   • Severity escalations (warning → critical) replace the old alert

3. Protocol status is derived from active alerts:

   • healthy → no alerts
   • degraded → warnings only
   • critical → any critical alert

[mijinummi]

Hello @feyishola , thanks for your contribution, please kindly resolve the conflict, and fix the remaining 1 ci that is failing. Well done for this great work!