M1-T05: drop location/poo database config from Settings and tests

Remove the dead location_database_url / poo_database_url fields and the
location_sqlite_path / poo_sqlite_path computed properties from Settings;
drop them from the config-page payload and from .env.example. Update the
test hardcodes (test_config, test_public_ip, test_smtp) and reduce the
conftest test_database_urls fixture to the single app DB. The one-time
migration script keeps reading legacy URLs from env/CLI, independent of
Settings.

pytest 95 passed; ruff clean (pre-existing only).

app/config.py

@@ -12,9 +12,6 @@ class Settings(BaseSettings):
     app_hostname: str = "localhost:8000"
     app_database_url: str = "sqlite:///./data/app.db"
 
-    location_database_url: str = "sqlite:///./data/locationRecorder.db"
-    poo_database_url: str = "sqlite:///./data/pooRecorder.db"
-
     ticktick_client_id: str = ""
     ticktick_client_secret: str = ""
     ticktick_token: str = ""
@@ -77,21 +74,11 @@ class Settings(BaseSettings):
         raw_path = database_url[len(prefix) :]
         return Path(raw_path)
 
-    @computed_field
-    @property
-    def location_sqlite_path(self) -> Path | None:
-        return self._sqlite_path_from_url(self.location_database_url)
-
     @computed_field
     @property
     def app_sqlite_path(self) -> Path | None:
         return self._sqlite_path_from_url(self.app_database_url)
 
-    @computed_field
-    @property
-    def poo_sqlite_path(self) -> Path | None:
-        return self._sqlite_path_from_url(self.poo_database_url)
-
     @computed_field
     @property
     def auth_cookie_secure(self) -> bool: