refactor(dbt): migrate to domain-scoped schema names

- Create generate_schema_name macro to use custom schema names directly
- Update dbt_project.yml schemas: staging→stg_toronto, intermediate→int_toronto, marts→mart_toronto
- Add dbt/macros/toronto/ directory for future domain-specific macros
- Fix documentation drift in PROJECT_REFERENCE.md (load-data-only→load-toronto-only)
- Update DATABASE_SCHEMA.md with new schema names
- Update CLAUDE.md database schemas table
- Update adding-dashboard.md runbook with domain-scoped pattern

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dbt/macros/generate_schema_name.sql

@@ -0,0 +1,11 @@
+-- Override dbt default schema name generation.
+-- Use the custom schema name directly instead of
+-- concatenating with the target schema.
+-- See: https://docs.getdbt.com/docs/build/custom-schemas
+{% macro generate_schema_name(custom_schema_name, node) %}
+    {%- if custom_schema_name is none -%}
+        {{ target.schema }}
+    {%- else -%}
+        {{ custom_schema_name | trim }}
+    {%- endif -%}
+{% endmacro %}