feat(views): saved-views backend — table, model, CRUD + reorder API

Per-user named snapshots of the feed's FeedFilters. New saved_views table
(migration 0035, unique per user+name, position, is_default) + SavedView
model, and a /api/saved-views router (list/create/patch/delete/reorder)
gated behind require_human so the shared demo account can't pollute it.
Setting is_default clears the flag on the user's other views (one default).

backend/app/routes/saved_views.py

@@ -0,0 +1,152 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import func, select, update
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session
+
+from app.auth import require_human
+from app.db import get_db
+from app.models import SavedView, User
+
+# Saved "smart views": per-user named snapshots of the feed's FeedFilters. Gated behind
+# require_human so the shared demo account can't pollute a communal list (mirrors how other
+# personal-state writes are scoped).
+router = APIRouter(prefix="/api/saved-views", tags=["saved-views"])
+
+
+def _serialize(v: SavedView) -> dict:
+    return {
+        "id": v.id,
+        "name": v.name,
+        "filters": v.filters or {},
+        "position": v.position,
+        "is_default": v.is_default,
+    }
+
+
+@router.get("")
+def list_views(
+    user: User = Depends(require_human), db: Session = Depends(get_db)
+) -> list[dict]:
+    rows = (
+        db.execute(
+            select(SavedView)
+            .where(SavedView.user_id == user.id)
+            .order_by(SavedView.position, SavedView.id)
+        )
+        .scalars()
+        .all()
+    )
+    return [_serialize(v) for v in rows]
+
+
+@router.post("")
+def create_view(
+    payload: dict,
+    user: User = Depends(require_human),
+    db: Session = Depends(get_db),
+) -> dict:
+    name = (payload.get("name") or "").strip()
+    if not name:
+        raise HTTPException(status_code=400, detail="name is required")
+    filters = payload.get("filters")
+    if not isinstance(filters, dict):
+        raise HTTPException(status_code=400, detail="filters must be an object")
+    maxpos = db.execute(
+        select(func.coalesce(func.max(SavedView.position), -1)).where(
+            SavedView.user_id == user.id
+        )
+    ).scalar_one()
+    view = SavedView(
+        user_id=user.id, name=name[:80], filters=filters, position=maxpos + 1
+    )
+    db.add(view)
+    try:
+        db.commit()
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=409, detail=f"You already have a view named “{name}”."
+        )
+    return _serialize(view)
+
+
+def _own_view(db: Session, user: User, view_id: int) -> SavedView:
+    view = db.get(SavedView, view_id)
+    if view is None or view.user_id != user.id:
+        raise HTTPException(status_code=404, detail="Unknown view")
+    return view
+
+
+@router.patch("/{view_id}")
+def update_view(
+    view_id: int,
+    payload: dict,
+    user: User = Depends(require_human),
+    db: Session = Depends(get_db),
+) -> dict:
+    view = _own_view(db, user, view_id)
+    if "name" in payload:
+        name = (payload.get("name") or "").strip()
+        if not name:
+            raise HTTPException(status_code=400, detail="name cannot be empty")
+        view.name = name[:80]
+    if "filters" in payload:
+        filters = payload.get("filters")
+        if not isinstance(filters, dict):
+            raise HTTPException(status_code=400, detail="filters must be an object")
+        view.filters = filters
+    if "is_default" in payload:
+        make_default = bool(payload.get("is_default"))
+        if make_default:
+            # At most one default per user: clear the flag on the others first.
+            db.execute(
+                update(SavedView)
+                .where(SavedView.user_id == user.id, SavedView.id != view.id)
+                .values(is_default=False)
+            )
+        view.is_default = make_default
+    try:
+        db.commit()
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(
+            status_code=409, detail=f"You already have a view named “{view.name}”."
+        )
+    return _serialize(view)
+
+
+@router.delete("/{view_id}")
+def delete_view(
+    view_id: int,
+    user: User = Depends(require_human),
+    db: Session = Depends(get_db),
+) -> dict:
+    view = _own_view(db, user, view_id)
+    db.delete(view)
+    db.commit()
+    return {"deleted": view_id}
+
+
+@router.post("/reorder")
+def reorder_views(
+    payload: dict,
+    user: User = Depends(require_human),
+    db: Session = Depends(get_db),
+) -> dict:
+    ids = payload.get("ids")
+    if not isinstance(ids, list):
+        raise HTTPException(status_code=400, detail="ids must be a list")
+    rows = (
+        db.execute(select(SavedView).where(SavedView.user_id == user.id))
+        .scalars()
+        .all()
+    )
+    by_id = {v.id: v for v in rows}
+    pos = 0
+    for vid in ids:
+        v = by_id.get(vid)
+        if v is not None:
+            v.position = pos
+            pos += 1
+    db.commit()
+    return {"ok": True}