v1.5.1: bootstrap fixes (git + ssh in container, Tailscale host rewrite, /opt/projects label)

- Dockerfile: install git + openssh-client in runtime image; pre-populate
  /root/.ssh/known_hosts with the Tailscale ssh-keyscan for
  100.114.205.53:2222 (Gitea SSH). Without these, the bootstrap push
  step from inside the container fails with "command not found" or
  host-key prompts.
- docker-compose.yml: mount ./secrets/boocode_gitea as
  /root/.ssh/id_ed25519:ro so the container can authenticate to Gitea
  over SSH for the initial push.
- .gitignore: add secrets/ so the keypair never lands in the repo.
- project_bootstrap.ts: rewrite the Gitea-returned ssh_url's hostname
  from git.indifferentketchup.com to 100.114.205.53 before adding it
  as origin, so the push hits the Tailscale interface that the
  known_hosts entry covers.
- CreateProjectModal.tsx: preview label now reads "Folder:
  /opt/projects/<name>" to match the new BOOTSTRAP_ROOT (was /opt/).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -14,6 +14,7 @@ services:
       # Writable mount only for the create-new-project bootstrap target.
       # Host must `mkdir -p /opt/projects` before container start.
       - /opt/projects:/opt/projects:rw
+      - ./secrets/boocode_gitea:/root/.ssh/id_ed25519:ro
     depends_on:
       - boocode_db
     networks: