test: suite pytest (36 tests) et CI Gitea Actions

Modèles (chemin DB, migration 0.1.0, ordre, réconciliation),
classification, client Gitea (pagination, en-tête, écritures),
API (CSRF, write-back, codes d'erreur, 502 propre), auth Basic
et fail-closed. Tous verts; pyflakes propre.

.gitea/workflows/ci.yml

@@ -0,0 +1,20 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - name: Install
+        run: pip install -e ".[dev]"
+      - name: Compile check
+        run: python -m py_compile app/*.py
+      - name: Tests
+        run: pytest -q