setup-container: chmod the binary and improve missing-binary hint

When downloading a release asset over HTTP the executable bit is lost,
so checking '-x' would always fail. Check existence instead and chmod
unconditionally. Update the error message to cover the three common
install paths.

lxc/setup-container.sh

@@ -30,11 +30,26 @@ if ! command -v microsocks >/dev/null 2>&1; then
     rm -rf "$tmp"
 fi
 
-# 3. Install fetch-service binary (forventes pushet ind af host-scriptet)
-if [[ ! -x /usr/local/bin/weircon-random-proxy ]]; then
-    echo "ERR: /usr/local/bin/weircon-random-proxy mangler — push den fra host'en først" >&2
+# 3. Install fetch-service binary.
+#    Forventes pushet/lagt på plads af brugeren før dette script køres
+#    (enten via `pct push` fra Proxmox-hosten, eller lokalt med `cp`).
+BIN=/usr/local/bin/weircon-random-proxy
+if [[ ! -f "$BIN" ]]; then
+    cat >&2 <<EOF
+ERR: $BIN mangler.
+
+Læg binæren på plads med én af:
+  - fra Proxmox-host:  pct push <ctid> ./weircon-random-proxy $BIN --perms 0755
+  - fra inde i LXC:    cp /path/to/weircon-random-proxy $BIN
+                       chmod +x $BIN
+  - download release:  curl -fLo $BIN https://<gitea>/<owner>/weircon-random-proxy/releases/download/<tag>/weircon-random-proxy
+                       chmod +x $BIN
+
+Kør derefter setup-container.sh igen.
+EOF
     exit 1
 fi
+chmod +x "$BIN"
 
 # 4. Helper-scripts
 install -Dm755 "$SCRIPT_DIR/netns-up.sh"   /usr/local/sbin/weircon-netns-up