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

README.md

@@ -1,4 +1,58 @@
 # company_site
 
-Django site for compan
-Somethinf
+Django site for AIML Operations.
+
+## Local development (uv)
+
+```bash
+uv sync
+cp .env.example .env
+cd company_site
+DJANGO_ENV=dev uv run python manage.py migrate
+DJANGO_ENV=dev uv run python manage.py runserver
+```
+
+## Docker (dev + Postgres)
+
+```bash
+cp .env.example .env
+docker compose up --build
+```
+
+App: http://localhost:8000
+
+## Environments
+
+Set `DJANGO_ENV` to one of:
+
+| Value | DEBUG default | Logging level |
+|-------|---------------|---------------|
+| `dev` | true | DEBUG |
+| `beta` | false | INFO |
+| `prod` | false | WARNING |
+
+Secrets and service config come from environment variables. See `.env.example`.
+
+## CI / deploy workflows
+
+| Workflow | Trigger | What runs |
+|----------|---------|-----------|
+| `.gitea/workflows/ci.yml` | Pull requests to `master` | Unit tests only |
+| `.gitea/workflows/deploy.yml` | Push to `master` | Unit tests → Docker build/test → deploy |
+
+Deploy never runs on pull requests. Uses separate workflow files (not job `if` conditions) so Gitea runners handle it reliably.
+
+## Production deploy
+
+Server keeps its own `.env` at the live site path. Deploy rsyncs code but **never overwrites `.env`**.
+
+1. On the server, copy `.env.prod.example` to `.env` and fill in production values.
+2. Run `bash scripts/validate-env.sh /path/to/.env` to verify required variables.
+3. Push to `master` — the deploy workflow runs `scripts/deploy.sh`, which:
+   - rsyncs checkout to live site (preserving `.env`)
+   - validates environment variables
+   - `docker compose -f docker-compose.prod.yml build`
+   - `docker compose up -d`
+   - runs migrations in the web container
+
+Legacy venv/systemd deploy: `DEPLOY_MODE=legacy bash scripts/deploy.sh <checkout>`.