fix(firewall): WireGuard peer-to-peer forward-Chain-Auto-Rule

Die forward-chain hatte policy=drop ohne Ausnahme für WireGuard-
Peer-to-Peer-Traffic. Pakete von Peer A nach Peer B (beide am
selben wg-Interface) müssen durch die Box forwarded werden — das
war bisher stiller Drop.

Lösung: loadView liest alle aktiven server-mode WG-Interfaces und
trägt sie in View.WGServerIfaces ein. Das Template emittiert pro
Interface iifname "<wg>" accept in der forward-chain. Return-Pakete
gehen bereits via ct state established durch.

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

internal/firewall/firewall.go

@@ -103,6 +103,14 @@ type View struct {
 	// Operator never edits these — they belong to the service. If
 	// the service is removed/disabled, the rule is gone next render.
 	AutoRules []AutoFWRule
+
+	// WGServerIfaces holds the interface names of all active
+	// WireGuard server-mode interfaces. The forward chain emits
+	// iifname "<iface>" accept for each — required so that peer-to-
+	// peer traffic (Peer A → Peer B both connected to the same wg
+	// interface) can be forwarded by the box. Without this, the
+	// forward policy=drop silently kills all inter-peer packets.
+	WGServerIfaces []string
 }
 
 // AutoFWRule is one auto-emitted inbound rule. Proto is "tcp" or
@@ -278,6 +286,19 @@ func (g *Generator) loadView(ctx context.Context) (*View, error) {
 	// ── Auto-Rules aus laufender Service-Config ──
 	view.AutoRules = g.loadAutoRules(ctx)
 
+	// ── WireGuard server-iface names (für forward-chain) ──
+	wgRows, err := g.Pool.Query(ctx,
+		`SELECT name FROM wireguard_interfaces WHERE active AND mode = 'server'`)
+	if err == nil {
+		defer wgRows.Close()
+		for wgRows.Next() {
+			var name string
+			if wgRows.Scan(&name) == nil {
+				view.WGServerIfaces = append(view.WGServerIfaces, name)
+			}
+		}
+	}
+
 	return view, nil
 }