M1-T04: converge startup chain onto the single app DB

run_all_migrations() now adopts/initializes only the app DB and returns
{'app': ...}. app/main.py drops the location/poo readiness checks
(ensure_location_db_ready / ensure_poo_db_ready) and their imports;
ensure_runtime_dirs only provisions the app DB path; lifespan still
fail-closes on a missing/unmanaged app DB. Delete the retired
location/poo adopt scripts and the alembic_location / alembic_poo
chains. Update tests to single-DB expectations and drop the obsolete
location/poo adoption + readiness tests.

pytest 95 passed; ruff clean (pre-existing only); a fresh app DB
initialized via scripts.run_migrations contains location + poo_records.

app/main.py

@@ -21,8 +21,6 @@ from app.services.auth import AuthBootstrapError, initialize_auth_schema
 from app.services.config_page import seed_missing_config_from_bootstrap, sync_app_hostname_from_bootstrap
 from app.services.public_ip import check_public_ipv4_and_notify
 from scripts.app_db_adopt import AppDatabaseAdoptionError, validate_app_runtime_db
-from scripts.location_db_adopt import LocationDatabaseAdoptionError, validate_location_runtime_db
-from scripts.poo_db_adopt import PooDatabaseAdoptionError, validate_poo_runtime_db
 
 
 def _run_scheduled_public_ip_check() -> None:
@@ -50,41 +48,16 @@ def ensure_auth_db_ready() -> None:
         session.close()
 
 
-def ensure_location_db_ready() -> None:
-    settings = get_settings()
-    if settings.location_sqlite_path is None:
-        return
-
-    try:
-        validate_location_runtime_db(settings.location_database_url)
-    except LocationDatabaseAdoptionError as exc:
-        raise RuntimeError(str(exc)) from exc
-
-
-def ensure_poo_db_ready() -> None:
-    settings = get_settings()
-    if settings.poo_sqlite_path is None:
-        return
-
-    try:
-        validate_poo_runtime_db(settings.poo_database_url)
-    except PooDatabaseAdoptionError as exc:
-        raise RuntimeError(str(exc)) from exc
-
-
 def ensure_runtime_dirs() -> None:
     settings = get_settings()
-    for path in (settings.app_sqlite_path, settings.location_sqlite_path, settings.poo_sqlite_path):
-        if path is not None:
-            path.parent.mkdir(parents=True, exist_ok=True)
+    if settings.app_sqlite_path is not None:
+        settings.app_sqlite_path.parent.mkdir(parents=True, exist_ok=True)
 
 
 @asynccontextmanager
 async def lifespan(_: FastAPI):
     ensure_runtime_dirs()
     ensure_auth_db_ready()
-    ensure_location_db_ready()
-    ensure_poo_db_ready()
     scheduler = BackgroundScheduler(timezone="UTC")
     scheduler.add_job(
         _run_scheduled_public_ip_check,