Add timezone support and auto-sync push subscriptions

- Install tzdata in Docker for proper Australia/Perth timezone handling
- Update VAPID email to standard placeholder
- Auto-sync browser push subscriptions to server on page load

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Dockerfile

@@ -33,6 +33,8 @@ RUN npm run build
 FROM node:20-slim AS runner
 WORKDIR /app
 
+RUN apt-get update && apt-get install -y tzdata && rm -rf /var/lib/apt/lists/*
+
 ENV NODE_ENV=production
 ENV NEXT_TELEMETRY_DISABLED=1
 ENV TZ=Australia/Perth