feat(fw): Models + Repos für Firewall-v2 (6 Entities)

Models (internal/models/):
* FirewallAddressObject (host|network|range|fqdn)
* FirewallAddressGroup mit MemberIDs gorm:"-"-Slice
* FirewallService (proto+ports, builtin-Flag)
* FirewallServiceGroup mit MemberIDs
* FirewallRule (v2-Shape, src/dst nullable refs, exactly-one-of-Validation
  in Handler-Layer)
* FirewallNATRule (kind=dnat|snat|masquerade, alle nullable)

Repos (internal/services/firewall/, ein Paket):
* AddressObjectsRepo, AddressGroupsRepo (mit Members-Junction-Ops)
* ServicesRepo (refused Update/Delete für builtin=TRUE Rows),
  ServiceGroupsRepo
* RulesRepo, NATRulesRepo
Jeweils Standard-CRUD; Group-Repos handhaben Members atomic in einer
TX (Update ersetzt komplette Membership).

Handler + Renderer-Rewrite + Frontend folgen in den nächsten
Commits.

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

internal/services/firewall/addressobjects.go

@@ -0,0 +1,103 @@
+package firewall
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
+)
+
+var ErrAddressObjectNotFound = errors.New("address object not found")
+
+type AddressObjectsRepo struct {
+	Pool *pgxpool.Pool
+}
+
+func NewAddressObjectsRepo(pool *pgxpool.Pool) *AddressObjectsRepo {
+	return &AddressObjectsRepo{Pool: pool}
+}
+
+const addrObjBaseSelect = `
+SELECT id, name, kind, value, description, created_at, updated_at
+FROM firewall_address_objects
+`
+
+func (r *AddressObjectsRepo) List(ctx context.Context) ([]models.FirewallAddressObject, error) {
+	rows, err := r.Pool.Query(ctx, addrObjBaseSelect+" ORDER BY name ASC")
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := make([]models.FirewallAddressObject, 0, 8)
+	for rows.Next() {
+		o, err := scanAddrObj(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, *o)
+	}
+	return out, rows.Err()
+}
+
+func (r *AddressObjectsRepo) Get(ctx context.Context, id int64) (*models.FirewallAddressObject, error) {
+	row := r.Pool.QueryRow(ctx, addrObjBaseSelect+" WHERE id = $1", id)
+	o, err := scanAddrObj(row)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrAddressObjectNotFound
+		}
+		return nil, err
+	}
+	return o, nil
+}
+
+func (r *AddressObjectsRepo) Create(ctx context.Context, o models.FirewallAddressObject) (*models.FirewallAddressObject, error) {
+	row := r.Pool.QueryRow(ctx, `
+INSERT INTO firewall_address_objects (name, kind, value, description)
+VALUES ($1, $2, $3, $4)
+RETURNING id, name, kind, value, description, created_at, updated_at`,
+		o.Name, o.Kind, o.Value, o.Description)
+	return scanAddrObj(row)
+}
+
+func (r *AddressObjectsRepo) Update(ctx context.Context, id int64, o models.FirewallAddressObject) (*models.FirewallAddressObject, error) {
+	row := r.Pool.QueryRow(ctx, `
+UPDATE firewall_address_objects SET
+   name = $1, kind = $2, value = $3, description = $4, updated_at = NOW()
+WHERE id = $5
+RETURNING id, name, kind, value, description, created_at, updated_at`,
+		o.Name, o.Kind, o.Value, o.Description, id)
+	out, err := scanAddrObj(row)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrAddressObjectNotFound
+		}
+		return nil, err
+	}
+	return out, nil
+}
+
+func (r *AddressObjectsRepo) Delete(ctx context.Context, id int64) error {
+	tag, err := r.Pool.Exec(ctx, `DELETE FROM firewall_address_objects WHERE id = $1`, id)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrAddressObjectNotFound
+	}
+	return nil
+}
+
+func scanAddrObj(row interface{ Scan(...any) error }) (*models.FirewallAddressObject, error) {
+	var o models.FirewallAddressObject
+	if err := row.Scan(
+		&o.ID, &o.Name, &o.Kind, &o.Value,
+		&o.Description, &o.CreatedAt, &o.UpdatedAt,
+	); err != nil {
+		return nil, err
+	}
+	return &o, nil
+}