feat: project bootstrap and structure

Sprint 1 initialization:
- Project directory structure (portfolio_app/, tests/, dbt/, data/, scripts/)
- CLAUDE.md with AI assistant context
- pyproject.toml with all dependencies
- docker-compose.yml for PostgreSQL 16 + PostGIS
- Makefile with standard targets
- Pre-commit configuration (ruff, mypy)
- Environment template (.env.example)
- Error handling foundation (PortfolioError hierarchy)
- Test configuration (conftest.py, pytest config)

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

.gitignore

@@ -1,4 +1,28 @@
-# ---> Python
+# ====================
+# Project-Specific
+# ====================
+
+# Processed data (generated, not source)
+data/*/processed/
+
+# Reports (generated)
+reports/
+
+# Backups
+backups/
+
+# Notebook exports
+notebooks/*.html
+
+# dbt
+dbt/target/
+dbt/dbt_packages/
+dbt/logs/
+
+# ====================
+# Python
+# ====================
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]