Support remote Ollama servers (or none) at install time

The bundled ollama service in docker-compose.yml moves behind a
new `local-ollama` profile, so docker compose only starts the
container when COMPOSE_PROFILES includes that profile.

install.sh now asks how PIP should reach Ollama:
  local   bundled in this compose stack (previous default)
  remote  point at an existing Ollama server URL
  none    no local AI, external providers only

The choice writes OLLAMA_MODE, LOCAL_LLM_BASE_URL, and
COMPOSE_PROFILES into .env.compose. The compose wrapper in
install.sh and update.sh sources the env file so subsequent
docker compose invocations honour the profile. The model-pull
wizard step and image pull are skipped when not in local mode.

The bundled image is also no longer in the unconditional pull
batch; remote/none deployments shouldn't have to download a
~1 GB image they'll never run.

Also fixes .gitignore so .env.compose.example is tracked (the
file is referenced by docker-compose.yml's header comment but
was being silently ignored by the broad .env.* rule).