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>

docker-entrypoint.sh

@@ -1,6 +1,32 @@
 #!/bin/sh
 set -e
 
+# ─── Validate required environment variables ───
+missing=""
+for var in NEXT_PUBLIC_SUPABASE_URL NEXT_PUBLIC_SUPABASE_ANON_KEY SUPABASE_SERVICE_ROLE_KEY NEXT_PUBLIC_APP_URL CRON_SECRET; do
+  eval val=\$$var
+  if [ -z "$val" ]; then
+    missing="$missing  - $var\n"
+  fi
+done
+
+if [ -n "$missing" ]; then
+  printf "ERROR: Missing required environment variables:\n%b\nSee .env.docker.example for reference.\n" "$missing" >&2
+  exit 1
+fi
+
+# Warn if placeholder values are still set
+placeholders_found=""
+case "$NEXT_PUBLIC_SUPABASE_ANON_KEY" in *your-anon-key*) placeholders_found="$placeholders_found  - NEXT_PUBLIC_SUPABASE_ANON_KEY\n" ;; esac
+case "$SUPABASE_SERVICE_ROLE_KEY" in *your-service-role-key*) placeholders_found="$placeholders_found  - SUPABASE_SERVICE_ROLE_KEY\n" ;; esac
+case "$NEXT_PUBLIC_SUPABASE_URL" in *your-project*) placeholders_found="$placeholders_found  - NEXT_PUBLIC_SUPABASE_URL\n" ;; esac
+case "$NEXT_PUBLIC_APP_URL" in *your-domain*) placeholders_found="$placeholders_found  - NEXT_PUBLIC_APP_URL\n" ;; esac
+case "$CRON_SECRET" in *generate-a-random-secret*) placeholders_found="$placeholders_found  - CRON_SECRET\n" ;; esac
+
+if [ -n "$placeholders_found" ]; then
+  printf "WARNING: These variables appear to contain placeholder values:\n%bPlease set them to real values before running in production.\n" "$placeholders_found" >&2
+fi
+
 # Replace build-time placeholder sentinels with runtime env vars in static JS bundles.
 # This allows a single pre-built image to work with any Supabase project.
 if [ -d /app/.next/static ]; then