feat: Kafka Consumer Lag Monitoring and Auto-Scaling Consumer Groups (#109)

[Mona-i]

Summary

Closes #109

Implements Kafka consumer lag monitoring and auto-scaling consumer groups as requested in issue #109.

Changes

New Files (9 files, 1364 insertions)

File	Purpose
\src/types/kafka.ts\	TypeScript types: \PartitionLag, \ConsumerGroupLag, \ScalingEvent, \ConsumerGroupScalingConfig, \ScalingStatus, \KafkaMonitoringState\
\src/store/kafkaSlice.ts\	Zustand store slice — upsert/set groups, scaling status, event ring-buffer (max 200), markRefreshed, setError, reset
\src/services/kafkaMonitoringService.ts\	Core logic: lag threshold derivation, auto-scaling decision engine (\computeTargetInstances), \�uildScalingEvent, demo data generator, dual demo/production \KafkaMonitoringProvider\ factory
\src/hooks/useKafkaMonitoring.ts\	Polling hook (default 15 s) — parallel fetch of lag + scaling statuses, client-side auto-scaling evaluation, \ riggerManualScale, \
efresh\
\src/components/kafka/LagStatusBadge.tsx\	Accessible colour-coded status pill (healthy / warning / critical) with animated pulse
\src/components/kafka/ConsumerGroupLagCard.tsx\	Per-group card — expandable partition table, summary stats, manual scale input, last-event footer
\src/components/kafka/ScalingHistoryTable.tsx\	Compact table of recent auto-scaling events
\src/components/kafka/KafkaMonitoringDashboard.tsx\	Top-level dashboard composing all Kafka components
\src/tests/kafkaMonitoring.test.ts\	32 unit tests covering all core logic, store mutations, demo service, and a performance guard

Testing

• 32/32 unit tests pass (
  px vitest run src/tests/kafkaMonitoring.test.ts)
• Build passes — \✓ Compiled successfully, \✓ Finished TypeScript, \✓ Generating static pages (11/11)\
• Zero type errors across all 9 new files (verified via diagnostics)
• Performance guard — 10 000 auto-scaling evaluations complete in < 100 ms (P99 target met)

Architecture

• Demo-first pattern (matches existing codebase) — zero network calls in demo mode, real HTTP calls in production
• Zustand store with 200-event ring-buffer for scaling history
• Polling interval configurable per hook instance (default 15 s)
• All components are accessible (role, aria-label, aria-expanded on interactive elements)