Map PAUSE_ENABLED into core compose for staged config overrides

The controller (freeshard-controller#368) flips shard_core settings on a
subset of shards by writing an override into that shard's core .env on every
converge. For that to reach shard_core, the core-version docker-compose.yml
must map the consuming env var with a safe default.

Add FREESHARD_APPS__LIFECYCLE__PAUSE_ENABLED=${PAUSE_ENABLED:-false} to the
shard_core service. The :-false guard means a shard whose .env omits the
override keeps the default (fleet behavior identical); a shard whose .env sets
PAUSE_ENABLED=true resolves pause_enabled=true after recreate. The flag already
exists and is env-overridable, so no shard_core code change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ClaydeCode

docker-compose.yml

@@ -65,6 +65,7 @@ services:
       - FREESHARD_TRAEFIK__ACME_EMAIL=${EMAIL:?}
       - FREESHARD_TRAEFIK__DISABLE_SSL=${DISABLE_SSL:-false}
       - FREESHARD_PATH_ROOT_HOST=${FREESHARD_DIR:?}
+      - FREESHARD_APPS__LIFECYCLE__PAUSE_ENABLED=${PAUSE_ENABLED:-false}
     depends_on:
       postgres:
         condition: service_healthy