Dockerize chat_backend + Ollama LAN + DB file storage (#6) (#7)

## Summary

Implements [chat_backend#6](#6) Part A:

- **uv** packaging (`pyproject.toml` + `uv.lock`), Docker/compose (dev + prod), entrypoint/validate-env, Gitea unit-test + auto-deploy workflows (mirror `scha`)
- Env-driven Django settings (`DJANGO_*`, `DATABASE_URL`, CSRF/CORS)
- **`OLLAMA_BASE_URL`** wired through all Ollama/LangChain clients (prod → `http://10.0.0.128:11434`)
- **DatabaseStorage** — prompt/document file blobs in Postgres (`StoredFile`), not container FS; RAG materializes temp paths for loaders
- ASGI via `gunicorn` + `UvicornWorker` (HTTP + WebSockets)

Companion server-infra PR registers `app_catalog` / `host_apps` (port **8003**).

## Test plan

- [ ] `uv sync && cd llm_be && SKIP_RAG_INIT=1 uv run python manage.py test`
- [ ] `docker compose build && docker compose up` against bundled Postgres
- [ ] Confirm Ollama calls use `OLLAMA_BASE_URL` (not hardcoded localhost)
- [ ] Upload a document / prompt file → row in `chat_backend_storedfile`, no disk under `media/`
- [ ] After server-infra merge + secret/Postgres/NPM: deploy via `deploy.sh --app chat_backend --env prod`Reviewed-on: #7

.gitea/workflows/unittests.yml

@@ -0,0 +1,35 @@
+name: Unit Tests
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: self-hosted
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Install dependencies
+        run: uv sync --frozen
+
+      - name: Run unit tests
+        env:
+          DJANGO_ENV: dev
+          DJANGO_SECRET_KEY: test-secret-key
+          DJANGO_DEBUG: "true"
+          DJANGO_ALLOWED_HOSTS: localhost,127.0.0.1,testserver
+          DATABASE_URL: ""
+          DB_HOST: ""
+          SKIP_RAG_INIT: "1"
+          OLLAMA_BASE_URL: http://127.0.0.1:11434
+        working-directory: llm_be
+        run: uv run python manage.py test