[M2] Wire Loki Handler into Components

[miciav]

Description

Connect Loki handler to runner, generator, and controller.

Files to modify

• lb_common/logging.py
• lb_runner/services/async_localrunner.py
• lb_plugins/plugins/dfaas/generator.py

Acceptance criteria

• All components push to Loki when configured
• Labels include component, host, run_id
• Existing flows work without Loki

Milestone: M2 - Loki Push Integration
Issue: 2.3

[miciav]

Loki handler wired into runner/controller/DFaaS: lb_runner/engine/runner.py, lb_app/services/run_service.py, lb_plugins/plugins/dfaas/generator.py.