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/models.py

@@ -593,6 +593,28 @@ class PlaylistItem(Base):
     playlist: Mapped["Playlist"] = relationship(back_populates="items")
 
 
+class SavedView(Base, TimestampMixin, UpdatedAtMixin):
+    """A per-user named snapshot of the feed's filter/sort state (a "smart view").
+
+    `filters` is the serialized FeedFilters JSON the frontend applies with one click.
+    `position` orders them in the sidebar (drag-reorder); `is_default` marks the one view
+    applied automatically on load — at most one per user, enforced by the API on set."""
+
+    __tablename__ = "saved_views"
+    __table_args__ = (UniqueConstraint("user_id", "name", name="uq_user_saved_view"),)
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    user_id: Mapped[int] = mapped_column(
+        ForeignKey("users.id", ondelete="CASCADE"), index=True
+    )
+    name: Mapped[str] = mapped_column(String(80))
+    filters: Mapped[dict] = mapped_column(JSON)
+    position: Mapped[int] = mapped_column(Integer, default=0, server_default="0")
+    is_default: Mapped[bool] = mapped_column(
+        Boolean, default=False, server_default="false"
+    )
+
+
 class Notification(Base):
     """A durable, server-backed per-user notification (the inbox center, phase 1).