v2.3.1 - Fix memory auto-save persistence

Bug Fix

Fixed memory auto-save not persisting captures after get_events, get_stats, stream_events, and health_check calls.

Root cause

• MemoryService.StartAsync catch block did not set _disabled = true on failure, so subsequent saves attempted file I/O to non-existent directories and silently failed
• All fire-and-forget memory save paths swallowed exceptions with empty catch {} blocks, making failures invisible

Changes

• Set _disabled = true in StartAsync catch block so failed startup correctly disables the service
• Added Directory.CreateDirectory guard in SaveCaptureAsync for defense-in-depth
• Replaced silent catch {} with logged warnings in all 4 fire-and-forget memory save paths (GetEvents, GetStats, StreamEvents, HealthCheck)

Full Changelog: v2.3.0...v2.3.1