chore: devcontainer pre-creates as vscode, resilient postStart script

.devcontainer/postStart.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# Post-start hook: copies SSH keys from the host into the container, then
+# adds the git host. Never fails the devcontainer run: any missing file on
+# the host (e.g. no id_rsa) must not abort the lifecycle command.
+set -u
+
+mkdir -p ~/.ssh
+
+for f in id_rsa id_rsa.pub known_hosts; do
+  cp -f "/mnt/host-ssh/$f" ~/.ssh/ 2>/dev/null || true
+done
+
+ssh-keyscan -t ed25519,rsa gitlab.jonas-miederer.com >> ~/.ssh/known_hosts 2>/dev/null || true
+
+chmod 700 ~/.ssh 2>/dev/null || true
+chmod 600 ~/.ssh/id_rsa 2>/dev/null || true
+chmod 644 ~/.ssh/id_rsa.pub ~/.ssh/known_hosts 2>/dev/null || true
+
+exit 0