feat(todo): sections, tasks and labels on the server (ADR 0033, D6)

Three more synced tables, each a sealed payload alone, as project's:
section, task and label; deleted with the person's space.

The migration only adds: the three tables (id uuid defaulting to
gen_random_uuid_v7(), spaceId, keyId, payload, nonce), each indexed on
spaceId and cascading with its space (ON DELETE CASCADE to
offline_sync_spaces), and the modules' version rows. Nothing is dropped
or changed.

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_server/migrations/migration_registry.txt

@@ -22,3 +22,4 @@
 20261025165103193-assistants
 20261026140330157-assistant-budgets
 20261101000019144-projects
+20261101000604776-tasks