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/alembic/versions/0035_saved_views.py

@@ -0,0 +1,59 @@
+"""per-user saved smart views
+
+Revision ID: 0035_saved_views
+Revises: 0034_blocked_channels
+Create Date: 2026-07-01
+
+Adds the `saved_views` table: per-user named snapshots of the feed's filter/sort state. Each
+row stores the serialized FeedFilters (JSON), a sidebar `position` for drag-reorder, and an
+`is_default` flag (at most one per user, enforced by the API) for the view applied on load.
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0035_saved_views"
+down_revision: Union[str, None] = "0034_blocked_channels"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "saved_views",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("user_id", sa.Integer(), nullable=False),
+        sa.Column("name", sa.String(length=80), nullable=False),
+        sa.Column("filters", sa.JSON(), nullable=False),
+        sa.Column(
+            "position", sa.Integer(), server_default=sa.text("0"), nullable=False
+        ),
+        sa.Column(
+            "is_default",
+            sa.Boolean(),
+            server_default=sa.text("false"),
+            nullable=False,
+        ),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.text("now()"),
+            nullable=False,
+        ),
+        sa.Column(
+            "updated_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.text("now()"),
+            nullable=False,
+        ),
+        sa.ForeignKeyConstraint(["user_id"], ["users.id"], ondelete="CASCADE"),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint("user_id", "name", name="uq_user_saved_view"),
+    )
+    op.create_index("ix_saved_views_user_id", "saved_views", ["user_id"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_saved_views_user_id", table_name="saved_views")
+    op.drop_table("saved_views")