feat(todo): filters in Todoist's language, and a view of each label (ADR 0033, D35)

A filter is a query read on the device, as the server sees no task, kept
sealed in `saved_filter`. Filters & labels is a screen of its own under
Browse; a label opens its tasks, and favourite filters and labels join
Browse's Favourites. D36 records what of Todoist's Pro stays out.

Whats-New: Filters: keep views like "today & p1", and open a label to see its tasks, under Browse in Filters & labels.
Whats-New-De: Filter: Speichere Ansichten wie „heute & p1“ und öffne ein Label, um seine Aufgaben zu sehen, in der Übersicht unter Filter & Labels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_client/lib/migrations/migration_registry.dart

@@ -7,6 +7,7 @@ import 'package:serverpod_database/serverpod_database.dart';
 part '20261101000019144-projects/migration.dart';
 part '20261101000604776-tasks/migration.dart';
 part '20261101180755366-settings/migration.dart';
+part '20261106183802735-filters/migration.dart';
 
 /// Migration registry for the client-side database.
 class MigrationRegistry {
@@ -16,6 +17,7 @@ class MigrationRegistry {
     _Migration20261101000019144_projects(),
     _Migration20261101000604776_tasks(),
     _Migration20261101180755366_settings(),
+    _Migration20261106183802735_filters(),
   ];
 
   /// List of all client-side database migration versions.