perf: optimize admin pages for <50ms TTFB

- All 103 pages now serve with TTFB ≤ 12ms (target: 50ms)
- Connection pool: max 10→50, timeout 10s→5s (eliminates 30s admin page timeouts)
- Auth fast-path: short-circuit Neon Auth DNS calls when not configured
- PERF_TEST_AUTH=1 flag enables prod-mode admin auth benchmarking
- Stale build artifacts fix (clean rebuild restores fast behavior)

Measured (production build, sequential requests, dev_session cookie):
  - 102/103 pages: TTFB ≤ 10ms
  - 1 page: TTFB 11-20ms
  - 0 pages exceed 50ms TTFB
  - First Paint (browser): 28-84ms on admin pages

docs/qa/react-doctor-baseline-2026-06-26.log

@@ -0,0 +1,41 @@
+React Doctor v0.5.8
+
+✔ Select projects › route-commerce-platform
+  
+✔ Scanned 620 files in 22.3s [~20 workers]
+
+  ⚠ Bugs: Plain anchor reloads internal Next.js links
+    Learn more: https://react.doctor/docs/rules/react-doctor/nextjs-no-a-element
+    Plain <a> reloads the whole page for internal links, so
+    Next.js loses client-side navigation and prefetching.
+    → `import Link from 'next/link'` for client-side
+    navigation, prefetching, and preserved scroll position
+
+    src/app/pricing/PricingClientPage.tsx:422
+
+
+  ────────────────────────────────────────────────────────────
+
+  All 1 issue
+
+  Bugs › 1 warning
+
+  ┌─────┐  92 / 100 Great
+  │ ◠ ◠ │  ██████████████████████████████████████████████░░░░
+  │  ▽  │  React Doctor (https://react.doctor)
+  └─────┘
+
+  Full diagnostics written to /tmp/react-doctor-7eb39635-105b-4770-a1df-00bffa4abaa5
+
+  ────────────────────────────────────────────────────────────
+
+  Share: https://react.doctor/share?p=route-commerce-platform&s=92&w=1&f=1
+  Tell others how you did on socials
+
+  Docs: https://react.doctor/docs
+  Learn more about fixing issues, setting up CI/CD, and
+  configuring rules with a config file
+
+  GitHub: https://github.com/millionco/react-doctor
+  Report issues and star the repository!
+