Dockerize Django app with dev/beta/prod env config and uv.

Replace hardcoded settings with environment-driven config, add Docker
compose for local and production deploys, migrate from pip to uv, and
split Gitea workflows so PRs run tests only while master pushes deploy.

.env.example

@@ -0,0 +1,37 @@
+# Local development environment file (copy to .env).
+# For production server values, use .env.prod.example instead.
+DJANGO_ENV=dev
+DJANGO_DEBUG=true
+DJANGO_SECRET_KEY=change-me-for-local-development
+DJANGO_ALLOWED_HOSTS=localhost,127.0.0.1,0.0.0.0
+
+# Database (docker-compose sets DATABASE_URL for the web service)
+DATABASE_URL=postgres://company_site:company_site@db:5432/company_site
+# DB_HOST=db
+# DB_PORT=5432
+# DB_NAME=company_site
+# DB_USER=company_site
+# DB_PASSWORD=company_site
+
+# Logging
+# DJANGO_LOG_LEVEL=DEBUG
+
+# Analytics
+TIANJI_ENABLED=false
+TIANJI_TRACKER_URL=https://tianji.aimloperations.com/tracker.js
+TIANJI_WEBSITE_ID=
+
+# reCAPTCHA
+RECAPTCHA_PUBLIC_KEY=
+RECAPTCHA_PRIVATE_KEY=
+
+# Email (SMTP2GO)
+EMAIL_HOST=mail.smtp2go.com
+EMAIL_HOST_USER=
+EMAIL_HOST_PASSWORD=
+EMAIL_PORT=2525
+EMAIL_USE_TLS=true
+
+# Gunicorn
+GUNICORN_WORKERS=2
+GUNICORN_BIND=0.0.0.0:8000