Add weekly coaching check-in cron script

scripts/run-weekly-checkins.sh reads the admin API key from .env and POSTs the
Phase 3 batch endpoint (/discovery/coaching/run); a weekly host crontab entry
(Mon 08:00) invokes it. Running weekly services all cadences since the endpoint
skips users who aren't due. README documents the install. Output logs to
data/coaching-cron.log (gitignored).

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

scripts/run-weekly-checkins.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Weekly coaching check-in batch (Phase 3). Reads the admin API key from .env
+# and POSTs the batch endpoint, which generates a check-in for every eligible
+# user whose cadence is due. Invoked by a weekly cron entry.
+#
+# Override the target with IMPACTFLOW_BASE_URL (defaults to the local container).
+set -euo pipefail
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+BASE="${IMPACTFLOW_BASE_URL:-http://localhost:8011}"
+LOG="$DIR/data/coaching-cron.log"
+
+KEY="$(grep '^IMPACTFLOW_API_KEY=' "$DIR/.env" | cut -d= -f2 | tr -d '\r\n')"
+if [[ -z "$KEY" ]]; then
+  echo "$(date -u +%FT%TZ) ERROR: IMPACTFLOW_API_KEY not found in $DIR/.env" >> "$LOG"
+  exit 1
+fi
+
+resp="$(curl -sS -m 120 -X POST -H "X-API-Key: $KEY" \
+  "$BASE/discovery/coaching/run" 2>&1 || echo '{"error":"curl failed"}')"
+echo "$(date -u +%FT%TZ) $resp" >> "$LOG"