feat(db): Phase 1 — DB-Schema, goose-Migrations, GORM-Models

Initialer Schema-Set (8 Migrationen, 13 Tabellen) für EdgeGuard v1:
users + audit_log + system_settings, ha_nodes, backends/domains/
routing_rules/tls_certs, forward_proxy_acls, wireguard_peers,
firewall_rules, dns_zones/dns_records, licenses. Migrations liegen
in internal/database/migrations/ (analog mail-gateway) und werden
per //go:embed ins Binary gepackt — keine separate SQL-Dateien im
.deb. ValidateMigrations + Test schützen vor Duplicate-Versionen
(mail-gateway 2026-05-08-Vorfall). GORM-Models für alle Tabellen,
sensible Felder (password_hash, private_key_enc) sind json:"-".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/models/dns.go

@@ -0,0 +1,30 @@
+package models
+
+import "time"
+
+type DNSZone struct {
+	ID          int64     `gorm:"primaryKey"               json:"id"`
+	Name        string    `gorm:"column:name;uniqueIndex"  json:"name"`
+	ZoneType    string    `gorm:"column:zone_type"         json:"zone_type"`
+	Description *string   `gorm:"column:description"       json:"description,omitempty"`
+	ManagedBy   string    `gorm:"column:managed_by"        json:"managed_by"`
+	Active      bool      `gorm:"column:active"            json:"active"`
+	CreatedAt   time.Time `gorm:"column:created_at"        json:"created_at"`
+	UpdatedAt   time.Time `gorm:"column:updated_at"        json:"updated_at"`
+}
+
+func (DNSZone) TableName() string { return "dns_zones" }
+
+type DNSRecord struct {
+	ID         int64     `gorm:"primaryKey"          json:"id"`
+	ZoneID     int64     `gorm:"column:zone_id"      json:"zone_id"`
+	Name       string    `gorm:"column:name"         json:"name"`
+	RecordType string    `gorm:"column:record_type"  json:"record_type"`
+	Value      string    `gorm:"column:value"        json:"value"`
+	TTL        int       `gorm:"column:ttl"          json:"ttl"`
+	Active     bool      `gorm:"column:active"       json:"active"`
+	CreatedAt  time.Time `gorm:"column:created_at"   json:"created_at"`
+	UpdatedAt  time.Time `gorm:"column:updated_at"   json:"updated_at"`
+}
+
+func (DNSRecord) TableName() string { return "dns_records" }