The integration no longer owns a database

The HA integration is now purely a client of the NestQuest API service
(Feature 18): the API owns the SQLite file, the migrations, and every
business rule, so keeping a second copy of that ownership inside the
integration meant two sources of truth for household state, dead
wiring (the startup backfill, the day-rollover materialization and
sweep listeners, the corrupt-DB handling, the admin-allowlist seeding)
and settings keys nothing consumes any more.

Removed the integration's re-export/DB shim modules (db, store,
migrations, schema, the five DAOs, completion, children,
quest_definitions, admin_allowlist, presence, presence_management,
materialize, recurrence, events, sweep); the bundled domain package at
custom_components/nestquest/core/ is untouched and remains the single
home of those engines.  Setup now builds only the API client, the
snapshot coordinator, and the SSE subscription, registers the one
complete_quest proxy, and forwards the platforms.  The options flow
keeps only the keys the client itself consumes (API base URL + panel
token, update interval, staleness, panel idle timeout); the horizon,
rollover, notification and admin-allowlist settings moved out with the
database (the API's settings store owns horizon/rollover, and the
automations take their behaviour from blueprint inputs).  The
integration-plane tests now script the panel route's payloads and SSE
frames instead of seeding a local database; the core-plane tests keep
their coverage with imports pointed at core directly.

tests/test_dao_rules.py

@@ -6,8 +6,8 @@ import sqlite3
 
 import pytest
 
-from custom_components.nestquest.dao_children import ChildrenDao
-from custom_components.nestquest.dao_rules import (
+from custom_components.nestquest.core.dao_children import ChildrenDao
+from custom_components.nestquest.core.dao_rules import (
     ScheduleRuleRecord,
     ScheduleRuleStorage,
     ScheduleRulesDao,
@@ -17,9 +17,9 @@ from custom_components.nestquest.dao_rules import (
     schedule_rule_from_storage,
     schedule_rule_to_storage,
 )
-from custom_components.nestquest.db import NestQuestDatabase
-from custom_components.nestquest.migrations import apply_migrations
-from custom_components.nestquest.recurrence import (
+from custom_components.nestquest.core.db import NestQuestDatabase
+from custom_components.nestquest.core.migrations import apply_migrations
+from custom_components.nestquest.core.recurrence import (
     RuleType,
     RuleValidationError,
     ScheduleRule,
@@ -341,7 +341,7 @@ def test_rule_delete_concurrent_with_definition_create_is_safe(
                 # delete task has been scheduled, so the create holds
                 # the connection lock while the delete queues behind
                 # it — then the create proceeds and wins.
-                import custom_components.nestquest.dao_rules as dao_rules
+                import custom_components.nestquest.core.dao_rules as dao_rules
 
                 original_validate = (
                     dao_rules.QuestDefinitionsDao._validate_rule_exists