Apply demo-activity-bot: Bruno, the synthetic public-walk generator

Adds a background demo user (`bruno`) plus two pg-boss jobs that generate
public trekking routes and activities in inner Berlin and prune them
after 14 days. Disabled by default everywhere; flip `DEMO_BOT_ENABLED`
only in prod.

- Schema: `synthetic` boolean on routes + activities
- `ensureDemoUser()` idempotent insert + badge on /users/bruno
- Generation gate: 07-21 Berlin local, p=0.12, 40-route cap in 14d
- Initial 4-walk backfill on first enable; retention via daily prune
- Prometheus gauges `demo_bot_synthetic_routes_total` / `_activities_total`
- Unit + DB-gated integration + E2E tests

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

infrastructure/docker-compose.yml

@@ -34,6 +34,13 @@ services:
       WAHOO_CLIENT_ID: ${WAHOO_CLIENT_ID:-}
       WAHOO_CLIENT_SECRET: ${WAHOO_CLIENT_SECRET:-}
       WAHOO_WEBHOOK_TOKEN: ${WAHOO_WEBHOOK_TOKEN:-}
+      # Demo-activity-bot (Bruno). Disabled by default everywhere; flip to
+      # "true" only in prod to let the background worker generate public
+      # demo routes + activities and prune old ones. Region is a JSON blob
+      # `{"bbox":[w,s,e,n]}`; retention is in days (default 14).
+      DEMO_BOT_ENABLED: ${DEMO_BOT_ENABLED:-}
+      DEMO_BOT_RETENTION_DAYS: ${DEMO_BOT_RETENTION_DAYS:-}
+      DEMO_BOT_REGION: ${DEMO_BOT_REGION:-}
     healthcheck:
       test: ["CMD-SHELL", "curl -sf http://localhost:3000/api/health || exit 1"]
       interval: 15s