fix: script portability and npm security updates

Scripts:
- stop.sh: replace Linux-only fuser with cross-platform lsof fallback
- start.sh: parameterize port (APP_PORT) and container name (dynamic lookup)
- app-dev-start.sh: cross-platform stat (GNU -c / BSD -f) and setpriv/su fallback
- deploy-compose.sh: parameterize Docker registry via DOCKER_REGISTRY env var
- harden-postgres.sh: make DB_USER and DB_NAME configurable via env vars

NPM security:
- next: 15.5.12 → 15.5.15 (fixes HTTP request smuggling CVE)
- nodemailer: 8.0.1 → 8.0.5 (fixes SMTP command injection CVEs)
- lodash-es: add pnpm override to force >=4.18.0 (fixes code injection + prototype pollution)

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

package.json

@@ -49,7 +49,8 @@
   "pnpm": {
     "overrides": {
       "flatted": "^3.4.2",
-      "picomatch": "^4.0.4"
+      "picomatch": "^4.0.4",
+      "lodash-es": "^4.18.0"
     }
   },
   "packageManager": "pnpm@9.14.2",