fix(proxy): graceful error handling when Supabase is unreachable

Wrap getUser() calls in proxy.ts with try/catch so the proxy doesn't
crash when the Supabase client can't connect. Without this, the proxy
fails silently and Next.js returns 404 for all locale-dependent routes
(/auth/sign-in, /join, etc.) because the locale rewrite never happens.

Dockerfile

@@ -4,7 +4,7 @@ WORKDIR /app
 
 # --- Install + Build in one stage ---
 FROM base AS builder
-ARG CACHE_BUST=7
+ARG CACHE_BUST=8
 COPY . .
 RUN pnpm install --no-frozen-lockfile
 ENV NEXT_TELEMETRY_DISABLED=1