Add EC2 Launch Template strain genesis for AWS horizontal scale.

Ship POST /api/v1/forge/launch-template with cloud-init user-data embedding genesis snapshot hash and strain card ID; first template-tagged auth pins SpreadGeneration=0 and ParentAgentID=template.

server/internal/spreadgenesis/launch_template.go

@@ -0,0 +1,44 @@
+package spreadgenesis
+
+import (
+	"strings"
+
+	"crypto-miner-server/internal/models"
+	"crypto-miner-server/internal/strategy"
+)
+
+const (
+	JoinLaneLaunchTemplate      = "launch_template"
+	LaunchTemplateParentAgentID = "template"
+)
+
+type AuthProbe struct {
+	JoinLane            string
+	ParentAgentID       string
+	GenesisSnapshotHash string
+}
+
+func IsFirstAuth(isNewAgent bool, auth AuthProbe) bool {
+	if !isNewAgent {
+		return false
+	}
+	if strings.TrimSpace(auth.GenesisSnapshotHash) != "" {
+		return true
+	}
+	if strings.EqualFold(strings.TrimSpace(auth.ParentAgentID), LaunchTemplateParentAgentID) {
+		return true
+	}
+	return strings.TrimSpace(auth.JoinLane) == JoinLaneLaunchTemplate
+}
+
+func ApplyFirstAuth(agent *models.Agent, isNewAgent bool, auth AuthProbe) {
+	if agent == nil || !IsFirstAuth(isNewAgent, auth) {
+		return
+	}
+	agent.ParentAgentID = LaunchTemplateParentAgentID
+	agent.SpreadGeneration = 0
+	agent.JoinLane = JoinLaneLaunchTemplate
+	if strings.TrimSpace(agent.SpreadStrain) == "" {
+		agent.SpreadStrain = strategy.SpreadStrainFromJoinLane(JoinLaneLaunchTemplate)
+	}
+}