feat: rate limit public routes; backfill v0.9.5 changelog for mobile audit

Sign-in/sign-up now throttle at 3 req/10s/IP via better-auth's built-in
rate limiter; /r/ and /s/ share links throttle at 60 req/min/IP via
proxy.ts using the existing Redis-backed limiter (Next 16's Proxy always
runs Node.js, no Edge-runtime blocker after all).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@epicure/web",
-  "version": "0.9.4",
+  "version": "0.9.6",
   "private": true,
   "scripts": {
     "dev": "next dev",