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.

internal/apps/agent/observability/traffic.go

@@ -199,6 +199,7 @@ func (aggregate *trafficAggregate) consume(line []byte) {
 		Host:         strings.TrimSpace(record.Host),
 		Path:         normalizeAccessLogPath(record.Path),
 		StatusCode:   record.Status,
+		BytesSent:    record.BytesSent,
 	})
 }