feat: docker compose dev environment

Replaces the bare-metal `composer run dev` workflow with a fully
containerized 9-service stack orchestrated by docker compose. Single
command brings up the full app — three subdomains (marketing /
account / admin) reachable via Traefik with TLS, MariaDB + Valkey
+ Mailpit + Vite HMR + Horizon + scheduler all wired in.

Components:
- docker-compose.yml: traefik, app (php-fpm), web (nginx), mariadb,
  valkey, mailpit, vite, horizon, scheduler.
- docker/: Dockerfiles, nginx config, entrypoint scripts.
- Makefile: convenience targets (up / down / logs / shell / migrate
  / seed / test / pint / etc).
- .env.docker.example: template for Docker-stack environment vars
  (separate from website/.env so bare-metal devs aren't disrupted).
- website/vite.config.ts: server.host / origin / hmr / cors hooks
  driven by VITE_HOST / VITE_ORIGIN / VITE_HMR_HOST so the same
  config serves both bare-metal and Docker.
- website/bootstrap/app.php: redirectGuestsTo() now uses
  request()->getScheme() so http: dev hosts don't get force-https
  redirects.
- composer.json: drops laravel/sail (replaced by this stack).
- docs/superpowers/specs/2026-04-25-docker-compose-dev-environment-design.md:
  full design spec.

Bare-metal `composer run dev` workflow stays usable for anyone who
prefers it — Docker stack reads .env.docker, doesn't fight
website/.env.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker/nginx/nginx.conf

@@ -0,0 +1,40 @@
+user nginx;
+worker_processes auto;
+error_log /var/log/nginx/error.log notice;
+pid /var/run/nginx.pid;
+
+events {
+    worker_connections 1024;
+    multi_accept on;
+}
+
+http {
+    include       /etc/nginx/mime.types;
+    default_type  application/octet-stream;
+
+    log_format main '$remote_addr - $remote_user [$time_local] '
+                    '"$request" $status $body_bytes_sent '
+                    '"$http_referer" "$http_user_agent" "$host"';
+
+    access_log /var/log/nginx/access.log main;
+
+    sendfile on;
+    tcp_nopush on;
+    tcp_nodelay on;
+    keepalive_timeout 65;
+    types_hash_max_size 2048;
+    server_tokens off;
+
+    # Traefik handles compression at the edge — leave it off here.
+    gzip off;
+
+    # 50M for file uploads (matches php upload_max_filesize)
+    client_max_body_size 50M;
+
+    # Upstream PHP-FPM
+    upstream php-upstream {
+        server app:9000;
+    }
+
+    include /etc/nginx/conf.d/*.conf;
+}