ci(release): bootstrap pkg before installing FreeBSD port deps

The FreeBSD 15.0 VM image used by vmactions/freebsd-vm@v1 ships a pkg
binary that fails to parse the current pkg.freebsd.org metadata, with:
  pkg: truncated reply for signature_fingerprintsoutput, wanted 0 bytes
  pkg: Repository FreeBSD-ports cannot be opened.

This breaks 'pkg install', failing every release run since 2026-04-24.
Run 'pkg bootstrap -f' + 'pkg update -f' first to refresh pkg and the
catalogue before installing build deps.

.github/workflows/release.yml

@@ -9,7 +9,7 @@ on:
   pull_request:
 
 env:
-  SIGN_PIPE_VER: "v0.1.2"
+  SIGN_PIPE_VER: "v0.1.3"
   GORELEASER_VER: "v2.14.3"
   PRODUCT_NAME: "NetBird"
   COPYRIGHT: "NetBird GmbH"
@@ -59,6 +59,10 @@ jobs:
           copyback: false
           release: "15.0"
           prepare: |
+            # Refresh pkg to handle metadata format changes on FreeBSD 15.0
+            env ASSUME_ALWAYS_YES=yes pkg bootstrap -f
+            pkg update -f
+
             # Install required packages
             pkg install -y git curl portlint go