feat: implement rapid asset draining detection module

[AbdulmujibOladayo]

Summary

Implements the Rapid Asset Draining detection module under src/modules/detection/draining/, following the same plain-TypeScript class pattern used by the existing ai/investigations module.

Files Added

File	Purpose
interfaces/draining.interface.ts	Types: BalanceSnapshot, DrainingEvent, DrainingAlert, DrainingDetectorOptions
draining.service.ts	DrainingService — records balance snapshots, performs velocity analysis, detects drain events, generates emergency alerts with auto-escalated severity
draining.module.ts	DrainingModule factory for creating configured service instances
draining.service.spec.ts	Unit tests: no-drain cases, threshold detection, severity escalation, history pruning, multi-address isolation
index.ts	Barrel export

Detection Logic

• A drain event fires when the wallet balance drops by ≥ drainThreshold (default 50 %) within the windowMs window (default 5 min).
• Severity escalation is automatic based on drain ratio and speed:
  • critical — ≥ 90 % drain in any speed, or ≥ 70 % within 60 s
  • high — ≥ 70 % drain at moderate speed, or ≥ 50 % within 60 s
  • medium — ≥ 50 % at slower pace
• Each event carries a DrainingAlert with human-readable title, description, indicators, and recommended actions.
• Injectable now clock for fully deterministic tests.

Acceptance Criteria Met

• Draining events detected via recordBalance / evaluate
• Alerts generated with indicators and recommended actions
• Severity escalated automatically based on ratio and velocity

Closes #143

[mijinummi]

Hi @AbdulmujibOladayo , thanks for your contribution, please kindly fix the lint, tests, typescript etc errors. You may pull from the main , fix and push back. Well done