reorganise layout of location_postcode table

Also renames the table as this will make it easier to migrate.

src/nominatim_api/sql/sqlalchemy_schema.py

@@ -2,7 +2,7 @@
 #
 # This file is part of Nominatim. (https://nominatim.org)
 #
-# Copyright (C) 2024 by the Nominatim developer community.
+# Copyright (C) 2025 by the Nominatim developer community.
 # For a full list of authors see the git log.
 """
 SQLAlchemy definitions for all tables used by the frontend.
@@ -67,15 +67,16 @@ class SearchTables:
             sa.Column('isaddress', sa.Boolean))
 
         self.postcode = sa.Table(
-            'location_postcode', meta,
+            'location_postcodes', meta,
             sa.Column('place_id', sa.BigInteger),
             sa.Column('parent_place_id', sa.BigInteger),
+            sa.Column('osm_id', sa.BigInteger),
             sa.Column('rank_search', sa.SmallInteger),
-            sa.Column('rank_address', sa.SmallInteger),
             sa.Column('indexed_status', sa.SmallInteger),
             sa.Column('indexed_date', sa.DateTime),
             sa.Column('country_code', sa.String(2)),
             sa.Column('postcode', sa.Text),
+            sa.Column('centroid', Geometry),
             sa.Column('geometry', Geometry))
 
         self.osmline = sa.Table(