Schema 1.2.0: meta.series_schemas registry; lower-case name checks

- meta.series_schemas (name, description, created_at, created_by), seeded
  with 'series'. FK series_db_schema_fkey from meta.series.db_schema: a
  series may only live in a registered schema, for every client.
  Unregistered schemas belong to the user and are never touched.
- CHECK series_schemas_name_check and series_table_name_check enforce the
  shared lower-case identifier rule in the database.
- meta.find_schema_problems() covers the registry and reports a registered
  schema that no longer exists; user schemas are not examined.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sql/03_tables.sql

@@ -135,6 +135,16 @@ CREATE TABLE meta.sessions (
     exchange_id character varying(12) NOT NULL
 );
 
+-- Registry of series schemas. A series may only live in a registered schema
+-- (FK from meta.series.db_schema, 04_indexes.sql). Every other schema in the
+-- database belongs to the user and is never touched by the clients.
+CREATE TABLE meta.series_schemas (
+    name text NOT NULL,
+    description text,
+    created_at timestamp with time zone NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    created_by text NOT NULL DEFAULT CURRENT_USER
+);
+
 CREATE TABLE meta.timezones (
     iana_name character varying(50) NOT NULL,
     display_name character varying(100) NOT NULL,