Summary

Switch network_system integration gates to KCENON_HAS_* macros.

5W1H Specification

• Who: network_system maintainers
• What: Replace BUILD_WITH_* integration checks
• Where: core/integration/metrics code paths
• When: TBD
• Why: Align integration gating with unified flag contract
• How: Include feature_flags header and update macros

Parent Issue

kcenon/common_system#223

Tasks

• Include feature_flags.h in integration entry points
• Replace BUILD_WITH_COMMON_SYSTEM / THREAD_SYSTEM / CONTAINER_SYSTEM / MONITORING_SYSTEM
  with KCENON_HAS_* equivalents
• Update docs to reference KCENON_* as primary macros

Acceptance Criteria

• All integration checks use KCENON_HAS_*
• Build behavior remains unchanged under existing CMake options