fix: self-hosting UX improvements — setup script, env validation, doc fixes

- Add setup.sh interactive script for guided .env configuration
- Add env var validation and placeholder detection to docker-entrypoint.sh
- Fix migration count (52 → 63) in SELF-HOSTING.md
- Align Docker image name to ghcr.io/erp-mafia/gnubok in docker-compose.yml
- Update README and SELF-HOSTING.md to reference setup.sh

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup.sh

@@ -0,0 +1,81 @@
+#!/bin/sh
+set -e
+
+echo "gnubok setup"
+echo "============"
+echo ""
+
+# ─── Check prerequisites ───
+ok=true
+if ! command -v docker >/dev/null 2>&1; then
+  echo "ERROR: docker is not installed. Install it from https://docs.docker.com/get-docker/"
+  ok=false
+fi
+if ! docker compose version >/dev/null 2>&1; then
+  echo "ERROR: docker compose is not available. Install Docker Compose v2+."
+  ok=false
+fi
+if [ "$ok" = false ]; then
+  exit 1
+fi
+
+# ─── Create .env file ───
+if [ -f .env ]; then
+  printf ".env already exists. Overwrite? [y/N] "
+  read -r answer
+  case "$answer" in
+    [yY]*) ;;
+    *) echo "Keeping existing .env. Exiting."; exit 0 ;;
+  esac
+fi
+
+if [ ! -f .env.docker.example ]; then
+  echo "ERROR: .env.docker.example not found. Are you in the gnubok directory?"
+  exit 1
+fi
+
+cp .env.docker.example .env
+
+# ─── Auto-generate CRON_SECRET ───
+if command -v openssl >/dev/null 2>&1; then
+  cron_secret=$(openssl rand -hex 32)
+else
+  cron_secret=$(head -c 32 /dev/urandom | od -An -tx1 | tr -d ' \n')
+fi
+sed -i.bak "s|generate-a-random-secret|${cron_secret}|" .env && rm -f .env.bak
+
+# ─── Prompt for Supabase values ───
+echo ""
+echo "Enter your Supabase project values (from Settings > API in the Supabase dashboard):"
+echo ""
+
+printf "NEXT_PUBLIC_SUPABASE_URL (e.g. https://abcdefgh.supabase.co): "
+read -r supabase_url
+if [ -n "$supabase_url" ]; then
+  sed -i.bak "s|https://your-project.supabase.co|${supabase_url}|" .env && rm -f .env.bak
+fi
+
+printf "NEXT_PUBLIC_SUPABASE_ANON_KEY: "
+read -r anon_key
+if [ -n "$anon_key" ]; then
+  sed -i.bak "s|your-anon-key|${anon_key}|" .env && rm -f .env.bak
+fi
+
+printf "SUPABASE_SERVICE_ROLE_KEY: "
+read -r service_key
+if [ -n "$service_key" ]; then
+  sed -i.bak "s|your-service-role-key|${service_key}|" .env && rm -f .env.bak
+fi
+
+printf "NEXT_PUBLIC_APP_URL [http://localhost:3000]: "
+read -r app_url
+app_url="${app_url:-http://localhost:3000}"
+sed -i.bak "s|https://your-domain.com|${app_url}|" .env && rm -f .env.bak
+
+echo ""
+echo "Done! .env has been configured."
+echo ""
+echo "Next steps:"
+echo "  1. Apply database migrations (see SELF-HOSTING.md section 3)"
+echo "  2. Run: docker compose up -d"
+echo ""