fix: make FRONTEND_BASE_URL configurable via environment variable in webhook_service.py

[tmdeveloper007]

Issue Description

The URL https://helpdeskaiv1.vercel.app is hardcoded in backend/services/webhook_service.py in build_slack_payload and build_teams_payload. This should be configurable via environment variable.

Expected Fix

Replace hardcoded URL with os.environ.get('FRONTEND_BASE_URL', 'https://helpdeskaiv1.vercel.app').

Files to Modify

• backend/services/webhook_service.py (lines 42, 101)