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.

custom_components/nestquest/services.py

@@ -54,7 +54,7 @@ def _require_runtime(hass: HomeAssistant, find_runtime: FindRuntime):
     runtime = find_runtime(hass)
     if runtime is None:
         raise HomeAssistantError(
-            "NestQuest has no live database; cannot run this service"
+            "NestQuest is not loaded; cannot run this service"
         )
     return runtime