feat(container): add SSH server and rassumfrassum for LSP multiplexing

- Install openssh-server and create SSH infrastructure in container
- Install rassumfrassum (LSP multiplexer) via Python venv
- Expose SSH port 2222 and mount user public key for TRAMP access
- Update compose.yml to map port 2222 and mount SSH_PUBKEY_PATH
- Document SSH setup and TRAMP /ssh: access method in README

Containerfile

@@ -3,6 +3,15 @@ FROM node:lts-bookworm-slim
 
 WORKDIR /app
 
+# SSH server for TRAMP /ssh: access
+RUN apt-get update && apt-get install -y --no-install-recommends openssh-server python3-venv python3-pip \
+    && rm -rf /var/lib/apt/lists/* \
+    && mkdir -p /var/run/sshd /root/.ssh \
+    && chmod 700 /root/.ssh \
+    && ssh-keygen -A \
+    && python3 -m venv /opt/rass && /opt/rass/bin/pip install --no-cache-dir rassumfrassum \
+    && ln -s /opt/rass/bin/rass /usr/local/bin/rass
+
 # Install dependencies first (better layer caching)
 COPY package.json package-lock.json ./
 RUN npm ci
@@ -10,6 +19,6 @@ RUN npm ci
 # Copy the rest of the project
 COPY . .
 
-EXPOSE 4321
+EXPOSE 4321 22
 
-CMD ["npm","run","dev","--","--host","0.0.0.0","--port","4321"]
+CMD ["/bin/sh","-lc","/usr/sbin/sshd && npm run dev -- --host 0.0.0.0 --port 4321"]