refactor: production-essentials hardening pass

Backend: structured logger, env-validated config, graceful SIGTERM/SIGINT
shutdown, per-IP rate limiter, per-tier scheduler concurrency latch, error
context on previously-silent catches, compiled-JS Dockerfile stage.

Frontend: lib/api.ts consolidates BACKEND_URL with lazy production-required
check, root + per-segment error.tsx / not-found.tsx / loading.tsx,
generateMetadata on park and ride pages, graceful fallback when backend is
unreachable, Plausible script gated on env vars.

Infra: CI runs lint + typecheck + tests on both packages before docker build,
compose adds healthchecks, log rotation, and memory limits; .env.example
documents every variable.

Cleanup: removed empty app/api/parks/ dir and 0-byte root parks.db, moved
wait-times-urls.txt into docs/, dropped an `as any` cast.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/park/[id]/ride/[slug]/loading.tsx

@@ -0,0 +1,17 @@
+export default function RideLoading() {
+  return (
+    <div style={{ minHeight: "100vh", background: "var(--color-bg)", padding: "32px 24px" }}>
+      <div style={{ maxWidth: 960, margin: "0 auto" }}>
+        <div className="skeleton" style={{ width: 160, height: 14, borderRadius: 4, marginBottom: 16 }} />
+        <div className="skeleton" style={{ width: 320, height: 28, borderRadius: 6, marginBottom: 24 }} />
+        <div className="skeleton" style={{ width: 100, height: 24, borderRadius: 999, marginBottom: 24 }} />
+        <div style={{ display: "flex", gap: 8, marginBottom: 16 }}>
+          {Array.from({ length: 3 }).map((_, i) => (
+            <div key={i} className="skeleton" style={{ width: 80, height: 32, borderRadius: 6 }} />
+          ))}
+        </div>
+        <div className="skeleton" style={{ width: "100%", height: 280, borderRadius: 8 }} />
+      </div>
+    </div>
+  );
+}