docs: Complete Phase 6 notebooks and Phase 7 documentation review

Phase 6 - Jupyter Notebooks (15 total):
- Overview tab: livability_choropleth, top_bottom_10_bar, income_safety_scatter
- Housing tab: affordability_choropleth, rent_trend_line, tenure_breakdown_bar
- Safety tab: crime_rate_choropleth, crime_breakdown_bar, crime_trend_line
- Demographics tab: income_choropleth, age_distribution, population_density_bar
- Amenities tab: amenity_index_choropleth, amenity_radar, transit_accessibility_bar

Phase 7 - Documentation:
- Updated CLAUDE.md with Sprint 9 completion status
- Added notebooks directory to application structure
- Expanded figures directory listing

Closes #71, #72, #73, #74, #75, #76, #77

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

notebooks/README.md

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+# Toronto Neighbourhood Dashboard - Notebooks
+
+Documentation notebooks for the Toronto Neighbourhood Dashboard visualizations. Each notebook documents how data is queried, transformed, and visualized using the figure factory pattern.
+
+## Directory Structure
+
+```
+notebooks/
+├── README.md              # This file
+├── overview/              # Overview tab visualizations
+├── housing/               # Housing tab visualizations
+├── safety/                # Safety tab visualizations
+├── demographics/          # Demographics tab visualizations
+└── amenities/             # Amenities tab visualizations
+```
+
+## Notebook Template
+
+Each notebook follows a standard two-section structure:
+
+### Section 1: Data Reference
+
+Documents the data pipeline:
+- **Source Tables**: List of dbt marts/tables used
+- **SQL Query**: The exact query to fetch data
+- **Transformation Steps**: Any pandas/python transformations
+- **Sample Output**: First 10 rows of the result
+
+### Section 2: Data Visualization
+
+Documents the figure creation:
+- **Figure Factory**: Import from `portfolio_app.figures`
+- **Parameters**: Key configuration options
+- **Rendered Output**: The actual visualization
+
+## Available Figure Factories
+
+| Factory | Module | Use Case |
+|---------|--------|----------|
+| `create_choropleth` | `figures.choropleth` | Map visualizations |
+| `create_ranking_bar` | `figures.bar_charts` | Top/bottom N rankings |
+| `create_stacked_bar` | `figures.bar_charts` | Category breakdowns |
+| `create_scatter` | `figures.scatter` | Correlation plots |
+| `create_radar` | `figures.radar` | Multi-metric comparisons |
+| `create_age_pyramid` | `figures.demographics` | Age distributions |
+| `create_time_series` | `figures.time_series` | Trend lines |
+
+## Usage
+
+1. Start Jupyter from project root:
+   ```bash
+   jupyter notebook notebooks/
+   ```
+
+2. Ensure database is running:
+   ```bash
+   make docker-up
+   ```
+
+3. Each notebook is self-contained - run all cells top to bottom.
+
+## Notebook Naming Convention
+
+`{metric}_{chart_type}.ipynb`
+
+Examples:
+- `livability_choropleth.ipynb`
+- `crime_trend_line.ipynb`
+- `age_pyramid.ipynb`