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.

docker-compose.prod.yml

@@ -0,0 +1,30 @@
+services:
+  db:
+    image: postgres:16-alpine
+    restart: unless-stopped
+    environment:
+      POSTGRES_DB: ${DB_NAME}
+      POSTGRES_USER: ${DB_USER}
+      POSTGRES_PASSWORD: ${DB_PASSWORD}
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${DB_USER} -d ${DB_NAME}"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+      start_period: 20s
+
+  web:
+    build: .
+    restart: unless-stopped
+    ports:
+      - "${WEB_PORT:-8000}:8000"
+    env_file:
+      - .env
+    depends_on:
+      db:
+        condition: service_healthy
+
+volumes:
+  postgres_data: