feat: add volatile cache system for ephemeral data
Phase 2 of Memory Management System - volatile memory tier:
- VolatileCacheService: Redis-backed TTL storage
- Volatile router with full CRUD operations
- Predefined namespaces: weather, news, financial, transit, traffic,
air_quality, sports, social, system, context, custom
- Each namespace has appropriate default TTL (1min to 1hr)
- Refresh schedule support via cron expressions
- Scheduler integration endpoint: GET /volatile/scheduled
Endpoints:
- GET/POST/DELETE /volatile/{namespace}/{key}
- GET/DELETE /volatile/{namespace}
- GET /volatile/stats
- GET /volatile/scheduled
- GET /volatile/namespaces
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>