feat(agent) multi-driver db monitoring, hot-plug config, release pipeline

internal/sender/payload.go

@@ -9,6 +9,16 @@ type SnapshotPayload struct {
 	CPUAvg  float64 `json:"cpu_avg"`
 	MemAvg  float64 `json:"mem_avg"`
 	DiskAvg float64 `json:"disk_avg"`
+	Uptime  uint64  `json:"uptime"`
 
-	Uptime uint64 `json:"uptime"`
+	HostID      string `json:"host_id,omitempty"`
+	Environment string `json:"environment,omitempty"`
+
+	// Optional — only present when DB monitoring is enabled.
+	// DBDriver is a numeric identifier: 1=mysql/mariadb 2=postgres 3=redis 4=mongodb 5=sqlite
+	DBDriver         *uint8   `json:"db_driver,omitempty"`
+	DBConnPct        *float64 `json:"db_conn_pct,omitempty"`
+	DBThreadsRunning *float64 `json:"db_threads_running,omitempty"`
+	DBSlowQueries    *uint64  `json:"db_slow_queries,omitempty"`
+	DBSizeBytes      *uint64  `json:"db_size_bytes,omitempty"`
 }