Implement P2 Resend email + PagerDuty Events v2 + Slack retry backoff

- Resend: HTML email with drift summary table and CTA button
- PagerDuty: Events API v2 with dedup_key, severity mapping, custom_details
- Slack: setTimeout retry on 429 rate limit instead of dropping

products/docker-init-db.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+set -e
+
+# Create per-product databases
+for db in dd0c_route dd0c_drift dd0c_alert dd0c_portal dd0c_cost dd0c_run; do
+  echo "Creating database: $db"
+  psql -v ON_ERROR_STOP=0 --username "$POSTGRES_USER" --dbname postgres -c "CREATE DATABASE $db;" 2>/dev/null || true
+done
+
+# Run migrations for each product
+run_migrations() {
+  local db=$1
+  local dir=$2
+  if [ -d "$dir" ]; then
+    for sql in "$dir"/*.sql; do
+      [ -f "$sql" ] || continue
+      echo "  $db ← $(basename $sql)"
+      psql -v ON_ERROR_STOP=0 --username "$POSTGRES_USER" --dbname "$db" -f "$sql" 2>/dev/null || true
+    done
+  fi
+}
+
+run_migrations dd0c_alert /migrations/03-alert
+run_migrations dd0c_portal /migrations/04-portal
+run_migrations dd0c_cost /migrations/05-cost
+run_migrations dd0c_run /migrations/06-run
+
+echo "All databases initialized."