feat(api): support traffic bytes tracking in edge access logs and refactor analytics models

- Add `bytes_sent` to `NodeAccessLog` on both Agent and Master Server.
- Create ClickHouse migration `202607120001_add_bytes_sent_to_node_access_logs.sql`.
- Refactor duplicate stats structs by centralizing them into `analyticsmodel` package with type aliases.
- Simplify access log store delegations and remove redundant mapping loops.
- Regenerate Swagger documentation.
- Update changelog index.md.

pkg/protocol/agent.go

@@ -151,6 +151,7 @@ type NodeAccessLog struct {
 	Host         string `json:"host"`
 	Path         string `json:"path"`
 	StatusCode   int    `json:"status_code"`
+	BytesSent    int64  `json:"bytes_sent"`
 }
 
 // BufferedObservabilityRecord is a buffered observability record.