feat(#374): add telemetry config to docker-compose and .env

- Add MOSAIC_TELEMETRY_* variables to .env.example with descriptions
- Pass telemetry env vars to api service in production compose
- Pass telemetry env vars to coordinator service in dev and swarm composes
- Swarm composes default to production URL (https://tel-api.mosaicstack.dev)
- Dev compose includes commented-out telemetry-api service placeholder
- All compose files default MOSAIC_TELEMETRY_ENABLED to false for safety

Refs #374

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/docker-compose.yml

@@ -51,6 +51,12 @@ services:
       LOG_LEVEL: ${LOG_LEVEL:-info}
       HOST: 0.0.0.0
       PORT: 8000
+      # Telemetry (task completion tracking & predictions)
+      MOSAIC_TELEMETRY_ENABLED: ${MOSAIC_TELEMETRY_ENABLED:-false}
+      MOSAIC_TELEMETRY_SERVER_URL: ${MOSAIC_TELEMETRY_SERVER_URL:-http://telemetry-api:8000}
+      MOSAIC_TELEMETRY_API_KEY: ${MOSAIC_TELEMETRY_API_KEY:-}
+      MOSAIC_TELEMETRY_INSTANCE_ID: ${MOSAIC_TELEMETRY_INSTANCE_ID:-}
+      MOSAIC_TELEMETRY_DRY_RUN: ${MOSAIC_TELEMETRY_DRY_RUN:-false}
     ports:
       - "8000:8000"
     healthcheck:
@@ -122,6 +128,29 @@ services:
       com.mosaic.service: "secrets-init"
       com.mosaic.description: "OpenBao auto-initialization sidecar"
 
+  # ======================
+  # Telemetry API (Optional - for local development)
+  # ======================
+  # Uncomment to run the telemetry API locally for self-contained development.
+  # For production, use an external telemetry API URL instead.
+  # telemetry-api:
+  #   image: git.mosaicstack.dev/mosaic/telemetry-api:latest
+  #   container_name: mosaic-telemetry-api
+  #   restart: unless-stopped
+  #   environment:
+  #     HOST: 0.0.0.0
+  #     PORT: 8000
+  #   ports:
+  #     - "8001:8000"
+  #   healthcheck:
+  #     test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
+  #     interval: 30s
+  #     timeout: 10s
+  #     retries: 3
+  #     start_period: 10s
+  #   networks:
+  #     - mosaic-network
+
 volumes:
   postgres_data:
     name: mosaic-postgres-data