refactor: multi-dashboard structural migration

- Rename dbt project from toronto_housing to portfolio
- Restructure dbt models into domain subdirectories:
  - shared/ for cross-domain dimensions (dim_time)
  - staging/toronto/, intermediate/toronto/, marts/toronto/
- Update SQLAlchemy models for raw_toronto schema
- Add explicit cross-schema FK relationships for FactRentals
- Namespace figure factories under figures/toronto/
- Namespace notebooks under notebooks/toronto/
- Update Makefile with domain-specific targets and env loading
- Update all documentation for multi-dashboard structure

This enables adding new dashboard projects (e.g., /football, /energy)
without structural conflicts or naming collisions.

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

docs/DATABASE_SCHEMA.md

@@ -116,16 +116,38 @@ erDiagram
 
 ## Schema Layers
 
-### Raw Schema
+### Database Schemas
 
-Raw data is loaded directly from external sources without transformation:
+| Schema | Purpose | Managed By |
+|--------|---------|------------|
+| `public` | Shared dimensions (dim_time) | SQLAlchemy |
+| `raw_toronto` | Toronto dimension and fact tables | SQLAlchemy |
+| `staging` | Staging models | dbt |
+| `intermediate` | Intermediate models | dbt |
+| `marts` | Analytical tables | dbt |
+
+### Raw Toronto Schema (raw_toronto)
+
+Toronto-specific tables loaded by SQLAlchemy:
 
 | Table | Source | Description |
 |-------|--------|-------------|
-| `raw.neighbourhoods` | City of Toronto API | GeoJSON neighbourhood boundaries |
-| `raw.census_profiles` | City of Toronto API | Census profile data |
-| `raw.crime_data` | Toronto Police API | Crime statistics by neighbourhood |
-| `raw.cmhc_rentals` | CMHC Data Files | Rental market survey data |
+| `dim_neighbourhood` | City of Toronto API | 158 neighbourhood boundaries |
+| `dim_cmhc_zone` | CMHC | ~20 rental market zones |
+| `dim_policy_event` | Manual | Policy events for annotation |
+| `fact_census` | City of Toronto API | Census profile data |
+| `fact_crime` | Toronto Police API | Crime statistics |
+| `fact_amenities` | City of Toronto API | Amenity counts |
+| `fact_rentals` | CMHC Data Files | Rental market survey data |
+| `bridge_cmhc_neighbourhood` | Computed | Zone-neighbourhood mapping |
+
+### Public Schema
+
+Shared dimensions used across all projects:
+
+| Table | Description |
+|-------|-------------|
+| `dim_time` | Time dimension (monthly grain) |
 
 ### Staging Schema (dbt)