ci: run pytest in all workflows — real unit job + Qdrant-backed integration job

- pr.yaml: new pytest job (unit tests only, integration deselected by marker)
- main.yaml / cron.yaml / tag.yaml: replace the build-only 'test' job with a
  real pytest unit job + an integration-test job that starts a Qdrant
  container sharing the job container's network namespace
  (--network container:$(hostname) — bypasses the Gitea runner bug with
  service containers), waits for /healthz, runs 'pytest -m integration',
  then tears down.
- build/build-push jobs now require [test, integration-test]; previously
  'test' was only a docker build and pytest never ran in CI.
- integration-test first cleans up any stale qdrant container (rerun-safe).
- setup-python SHA aligned with docker-build.yaml (v7, python 3.13/3.14).

.gitea/workflows/pr.yaml

@@ -14,9 +14,25 @@ jobs:
         with:
           dockerfile: pkg/Dockerfile
 
+  pytest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7
+        with:
+          python-version: "3.13"
+      - name: Install dependencies
+        run: pip install -r requirements.txt pytest
+      - name: Run unit tests
+        run: pytest tests/ -v
+        env:
+          # indexer/server read env at import; unit tests need no real backend
+          QDRANT_URL: http://localhost:6333
+          COLLECTION_NAME: test
+
   build-test:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
       - uses: docker/setup-buildx-action@f87e5991a6d7451dcb8d9637bfbc97413f497069 # v4
-      - run: docker build -f pkg/Dockerfile -t ci-image:${{ github.sha }} .
+      - run: docker build -f pkg/Dockerfile -t ci-image:${{ github.sha }} .