Add nocodb-init container for automatic database registration

Follows the listmonk-init pattern: an alpine:3 container that runs once
after NocoDB is healthy, calls the REST API to register changemaker_v2
as a browsable data source, and exits. Idempotent — exits immediately
if the base already has tables, and guards against duplicate sources
during async table discovery.

Bunker Admin

.env.example

@@ -106,6 +106,7 @@ REPRESENT_API_URL=https://represent.opennorth.ca
 # --- NocoDB v2 (read-only data browser) ---
 # NocoDB uses its own database (nocodb_meta) to avoid conflicts with Prisma
 # The database is auto-created by init-nocodb-db.sh on first PostgreSQL startup
+# nocodb-init container auto-registers changemaker_v2 as a browsable data source
 NOCODB_V2_PORT=8091
 NOCODB_URL=http://changemaker-v2-nocodb:8080
 NOCODB_PORT=8091