feat(agent): packaging Windows + téléchargement HTTPS

- Téléchargement des binaires Tailscale Windows via download-tailscale-bins.sh
- Build Windows/Linux via build.sh avec génération d’archive zip
- Caddyfile : serve les agents en HTTPS sous /studioE5-agent*
- .gitignore : ignore agent/tailscale-bin/
- Documentation du téléchargement dans SUIVI_VPN_ONDEMAND.md

agent/download-tailscale-bins.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+set -e
+
+# Télécharge les binaires Tailscale Windows depuis l'installateur MSI officiel.
+# Nécessite: curl, msitools (msiextract)
+
+VERSION="${1:-1.98.4}"
+ARCH="amd64"
+OUTDIR="$(dirname "$0")/tailscale-bin/windows"
+MSI_URL="https://pkgs.tailscale.com/stable/tailscale-setup-${VERSION}-${ARCH}.msi"
+TMPDIR="$(mktemp -d)"
+
+cleanup() {
+    rm -rf "$TMPDIR"
+}
+trap cleanup EXIT
+
+echo "Downloading Tailscale ${VERSION} Windows installer..."
+curl -L -o "$TMPDIR/tailscale-setup.msi" "$MSI_URL"
+
+echo "Extracting binaries..."
+mkdir -p "$TMPDIR/extract"
+msiextract -C "$TMPDIR/extract" "$TMPDIR/tailscale-setup.msi" >/dev/null
+
+echo "Installing to ${OUTDIR}..."
+mkdir -p "$OUTDIR"
+cp "$TMPDIR/extract/PFiles64/Tailscale/tailscale.exe" "$OUTDIR/"
+cp "$TMPDIR/extract/PFiles64/Tailscale/tailscaled.exe" "$OUTDIR/"
+cp "$TMPDIR/extract/PFiles64/Tailscale/wintun.dll" "$OUTDIR/"
+
+echo "Done. Installed:"
+ls -lh "$OUTDIR"