Dockerize Django app with dev/beta/prod env config and uv (#6)

## Summary

- Containerize the Django app with Docker and docker-compose (dev + production)
- Refactor settings into `dev` / `beta` / `prod` environments driven by environment variables
- Connect to PostgreSQL via `DATABASE_URL` or `DB_*` vars
- Migrate package management from pip to uv (`pyproject.toml`, `uv.lock`)
- Split Gitea workflows: PRs run unit tests only; pushes to `master` run tests, Docker validation, and deploy
- Update deploy script to rsync code, preserve server `.env`, validate config, and run Docker compose

Closes #4

## Test plan

- [x] `uv run python manage.py test` passes locally (10/10)
- [x] `DJANGO_ENV=beta` and `DJANGO_ENV=prod` load with correct logging levels
- [x] `scripts/validate-env.sh` rejects missing production variables
- [ ] `docker compose up --build` starts app + Postgres locally
- [ ] Containerized unit tests pass in CI Docker job
- [ ] Server `.env` created from `.env.prod.example` before first production deploy
- [ ] CI workflow runs on this PR (tests only, no deploy)

Reviewed-on: #6

pyproject.toml

@@ -0,0 +1,26 @@
+[project]
+name = "company-site"
+version = "0.1.0"
+description = "Django site for AIML Operations"
+readme = "README.md"
+requires-python = ">=3.12"
+dependencies = [
+    "django==5.0",
+    "django-enum==2.1.0",
+    "django-phonenumber-field==8.0.0",
+    "django-recaptcha==4.0.0",
+    "gunicorn==23.0.0",
+    "phonenumbers==9.0.0",
+    "psycopg2-binary==2.9.10",
+    "python-dateutil==2.9.0.post0",
+    "typing-extensions==4.8.0",
+    "whitenoise==6.9.0",
+]
+
+[dependency-groups]
+dev = [
+    "pre-commit==4.1.0",
+]
+
+[tool.uv]
+package = false