feat: implement watch command

[overtrue]

Description

Implement the watch command for monitoring S3 bucket events in real-time.

Requirements

• Subscribe to bucket notifications (object created, deleted, etc.)
• Support event filtering by prefix/suffix
• Requires S3 Bucket Notifications feature support

Acceptance Criteria

• rc watch <bucket> - Watch for events on a bucket
• Support event type filtering (--events create,delete)
• Support prefix/suffix filtering (--prefix, --suffix)
• Return EXIT_UNSUPPORTED_FEATURE (7) when Notifications is not supported
• Support --force flag to bypass capability detection

Notes

This is a capability-dependent feature. Requires the storage provider to support S3 Bucket Notifications or compatible event streaming.