[S6] Add manual reconciliation API endpoint

[krakenhavoc]

Description

REST endpoint to trigger manual reconciliation for a specific repo.

Endpoint

POST /v1/integrations/github/repos/:id/reconcile

Requirements

• Auth: KrakenKey API key or session (existing auth guards)
• Enqueues reconciliation job (same queue as webhook-triggered)
• Returns job ID for status tracking
• Rate limit: max 1 manual reconciliation per repo per 5 minutes

Acceptance Criteria

• Endpoint triggers reconciliation
• Returns job ID
• Rate limited to prevent abuse
• Auth required