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.

app/routers/collections.py

@@ -304,7 +304,6 @@ async def duplicate_collection_api(request: Request, collection_id: int):
             )
 
         # ── Pages (rows) with property ids remapped to the copy's properties ──
-        proxies = {}
         prows = conn.execute(
             "SELECT * FROM collection_pages WHERE collection_id=? ORDER BY position",
             (collection_id,),
@@ -554,7 +553,7 @@ async def create_property_api(request: Request, collection_id: int):
             )
             conn.commit()
         except Exception:
-            raise HTTPException(status_code=409, detail=f"Property '{name}' already exists")
+            raise HTTPException(status_code=409, detail=f"Property '{name}' already exists") from None
 
     return {"id": cur.lastrowid, "name": name, "prop_type": prop_type, "status": "created"}
 
@@ -980,7 +979,7 @@ async def check_dependencies(request: Request, collection_id: int, page_id: int)
     except Exception:
         body = {}
 
-    new_status = body.get("new_status", "Done")
+    body.get("new_status", "Done")
 
     with get_conn() as conn:
         page = conn.execute("SELECT property_values_json FROM collection_pages WHERE id=?", (page_id,)).fetchone()
@@ -1070,7 +1069,7 @@ async def add_data_source(request: Request, collection_id: int):
             )
             conn.commit()
         except sqlite3.IntegrityError:
-            raise HTTPException(status_code=409, detail="This data source already exists in this collection")
+            raise HTTPException(status_code=409, detail="This data source already exists in this collection") from None
 
     return {
         "id": cur.lastrowid,
@@ -1109,7 +1108,7 @@ async def create_linked_database(request: Request, collection_id: int):
         body = {}
 
     name = body.get("name", "").strip()
-    new_workspace_id = body.get("workspace_id")
+    body.get("workspace_id")
 
     with get_conn() as conn:
         source = conn.execute(
@@ -1341,7 +1340,7 @@ async def add_page_dependency(request: Request, collection_id: int, page_id: int
             )
             conn.commit()
         except sqlite3.IntegrityError:
-            raise HTTPException(status_code=409, detail="This dependency already exists")
+            raise HTTPException(status_code=409, detail="This dependency already exists") from None
     return {"id": cur.lastrowid, "page_id": page_id, "dependency_id": dependency_id, "status": "added"}
 
 
@@ -1604,7 +1603,7 @@ def _render_gallery(view_type: str, collection: dict, pages: list[dict], config:
         cover_url = config.get("cover_property")
         cover_html = ""
         if cover_url:
-            for k, v in props.items():
+            for _k, v in props.items():
                 if isinstance(v, list) and len(v) > 0:
                     url = v[0].get("url", "") if isinstance(v[0], dict) else str(v[0])
                     if url.startswith("http"):
@@ -1674,7 +1673,7 @@ def _render_timeline(view_type: str, collection: dict, pages: list[dict], config
     for p in pages:
         props = json.loads(p.get("property_values_json", "{}"))
         start_val = end_val = None
-        for k, v in props.items():
+        for _k, v in props.items():
             if isinstance(v, str) and v.startswith("20"):
                 if "..." in v:
                     parts = v.split("...")
@@ -1847,7 +1846,7 @@ def _render_map(view_type: str, collection: dict, pages: list[dict], config: dic
     for p in pages:
         props = json.loads(p.get("property_values_json", "{}"))
         lat, lng = None, None
-        for k, v in props.items():
+        for _k, v in props.items():
             if isinstance(v, str) and "," in v:
                 parts = v.split(",")
                 try:
@@ -1914,7 +1913,7 @@ def _render_gantt(view_type: str, collection: dict, pages: list[dict], config: d
         props = json.loads(p.get("property_values_json", "{}"))
         group = None
         start_val = end_val = None
-        for k, v in props.items():
+        for _k, v in props.items():
             if isinstance(v, str) and v.startswith("20"):
                 if "→" in v:
                     parts = v.split("→")