homelable: preserve MCP server config across updates (#14996)

* homelable: preserve MCP server config across updates

The update path runs CLEAN_INSTALL=1 fetch_and_deploy_gh_release, which
wipes /opt/homelable before redeploying. The backup/restore only covers
backend/.env and data/, so an optionally-installed MCP server (set up via
Pouzor/homelable's own scripts/lxc-mcp-install.sh, which targets exactly
this LXC and lives in /opt/homelable/mcp) loses its .env and .venv on
every update. The homelable-mcp service then keeps running on deleted
inodes and dies at the next restart.

Back up mcp/.env when present, and after the deploy restore it, rebuild
the venv (same uv pattern as the backend), restore ownership and restart
the service. Fully conditional: installs without the MCP are unaffected.

* homelable: remove comments per maintainer review

ct/homelable.sh

@@ -38,6 +38,9 @@ function update_script() {
     msg_info "Backing up Configuration and Data"
     cp /opt/homelable/backend/.env /opt/homelable.env.bak
     cp -r /opt/homelable/data /opt/homelable_data_bak
+    if [[ -f /opt/homelable/mcp/.env ]]; then
+      cp -a /opt/homelable/mcp/.env /opt/homelable-mcp.env.bak
+    fi
     msg_ok "Backed up Configuration and Data"
 
     CLEAN_INSTALL=1 fetch_and_deploy_gh_release "homelable" "Pouzor/homelable" "tarball" "latest" "/opt/homelable"
@@ -61,6 +64,19 @@ function update_script() {
     rm -rf /opt/homelable_data_bak
     msg_ok "Restored Configuration and Data"
 
+    if [[ -f /opt/homelable-mcp.env.bak ]]; then
+      msg_info "Restoring MCP Server"
+      cp -a /opt/homelable-mcp.env.bak /opt/homelable/mcp/.env
+      rm -f /opt/homelable-mcp.env.bak
+      MCP_OWNER=$(stat -c '%U' /opt/homelable/mcp/.env)
+      cd /opt/homelable/mcp
+      $STD uv venv --clear /opt/homelable/mcp/.venv
+      $STD uv pip install --python /opt/homelable/mcp/.venv/bin/python -r requirements.txt
+      chown -R "$MCP_OWNER":"$MCP_OWNER" /opt/homelable/mcp
+      systemctl restart homelable-mcp
+      msg_ok "Restored MCP Server"
+    fi
+
     msg_info "Starting Service"
     systemctl start homelable
     msg_ok "Started Service"