feat: HA-Cluster v1.2.x — Split-Brain, TOTP, Enterprise-FW, Drift-Fix, VIP-Recovery

- keepalived: pg_role='standby' hat Vorrang vor role für BACKUP-Bestimmung
- keepalived-master.sh: gecrasht Dienste beim MASTER-Übergang starten (nicht nur reload)
- confighash: ip_addresses per Interface-Name hashen statt per FK (Cross-Node-Drift-Fix)
- TOTP/2FA: RFC 6238 — Setup-Flow, QR-Code, Admin-Disable; two-step Login
- Firewall-UI: Enterprise-Design — auto-Beschreibung, icon-only Actions, zero-hit Indikator
- fe80-Filter: Link-local IPv6 aus NTP/DNS Listen-Dropdowns entfernen
- VIP-Dashboard, Dual-Path VRRP, GW-Tracking (Migrations 0033/0034)
- Forward Proxy + DNS erweiterte Einstellungen (Migrations 0031/0032)
- unbound-control: edgeguard in unbound-Gruppe via postinst

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/handlers/users.go

@@ -35,6 +35,7 @@ func (h *UsersHandler) Register(rg *gin.RouterGroup) {
 	g.PUT("/:id", h.Update)
 	g.POST("/:id/password", h.SetPassword)
 	g.DELETE("/:id", h.Delete)
+	g.DELETE("/:id/totp", h.DisableTOTP)
 }
 
 func (h *UsersHandler) List(c *gin.Context) {
@@ -164,3 +165,22 @@ func (h *UsersHandler) Delete(c *gin.Context) {
 		c.Param("id"), nil, h.NodeID)
 	response.OK(c, gin.H{"ok": true})
 }
+
+// DisableTOTP allows an admin to disable 2FA for any user.
+func (h *UsersHandler) DisableTOTP(c *gin.Context) {
+	id, ok := parseID(c)
+	if !ok {
+		return
+	}
+	if err := h.Repo.DisableTOTP(c.Request.Context(), id); err != nil {
+		if errors.Is(err, users.ErrNotFound) {
+			response.NotFound(c, err)
+			return
+		}
+		response.Internal(c, err)
+		return
+	}
+	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "user.totp.disabled",
+		c.Param("id"), nil, h.NodeID)
+	response.OK(c, gin.H{"ok": true})
+}