feat(schedules): auto-update stacks by Stack Label (#1717)

* feat(schedules): auto-update stacks by Stack Label

Add a reusable selector_type/selector_value on scheduled tasks so admins
can schedule image updates against live Stack Label membership across the
fleet or one node, reusing fleet label resolution and the existing
auto-update orchestrator.

* fix(image-updates): sanitize auto-update execute failure logs

Use a static format string and sanitizeForLog so CodeQL no longer
flags user-controlled stack names and error text in the execute catch.

* fix(ui): space Scope label from fleet/node segmented control

Match the Schedule row layout so the inline SegmentedControl no longer
sits flush against the Scope label.

* fix(ui): remove redundant wrapper around Scope segmented control

backend/src/__tests__/database-cascade.test.ts

@@ -41,6 +41,8 @@ const SCHEMA = `
     prune_targets TEXT,
     target_services TEXT,
     prune_label_filter TEXT,
+    selector_type TEXT,
+    selector_value TEXT,
     FOREIGN KEY(node_id) REFERENCES nodes(id)
   );