feat(v5.2.0): finalize Infrastructure & Polish (tests isolation, xdist, lint, CI)

tests/conftest.py: mutate the settings singleton (instead of rebinding) so DB + backup dir are isolated per test -> pytest-xdist safe.
Real backup tests (snapshot/prune/admin API) and OAuth mock tests (Gitea/GitHub/link) replace the previous skips.
init_db() now also creates webhook_subscriptions (full schema without the FastAPI lifespan).
ruff check is clean; .eslintrc.json migrated to eslint.config.mjs (flat config).
CI: lint job (ruff + eslint), parallel tests (-n auto), run on every branch push.
VERSION 5.11.1.

pyproject.toml

@@ -1,10 +1,10 @@
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 pythonpath = ["."]
-# Parallel execution via pytest-xdist (v5.2.0). Override with `-n 0` to run
-# sequentially: `pytest -n 0`.
-# Note: some tests use shared temp directories — run sequentially for stability.
-addopts = "-n 0"
+# Parallel execution (pytest-xdist) is OPT-IN so a bare `pytest` never fails
+# when xdist is not installed. Run locally with `pytest -n auto`; CI passes
+# `-n auto` explicitly after installing requirements-dev.txt.
+
 
 [tool.ruff]
 target-version = "py312"
@@ -18,4 +18,18 @@ select = ["E", "F", "I", "UP", "B", "W"]
 ignore = ["E501", "UP035"]
 
 [tool.ruff.lint.isort]
-known-first-party = ["app", "tests"]
+known-first-party = ["app", "tests"]
+
+[tool.ruff.lint.flake8-bugbear]
+# FastAPI requires dependency markers (Depends, Query, ...) in argument
+# defaults — that is not the bug B008 warns about.
+extend-immutable-calls = [
+  "fastapi.Depends",
+  "fastapi.Query",
+  "fastapi.Path",
+  "fastapi.Body",
+  "fastapi.Form",
+  "fastapi.File",
+  "fastapi.Header",
+  "fastapi.Cookie",
+]