feat(portfolio): tax strategy module — QBI deduction, passive activity loss, 1031 exchange

[paruff]

Problem

Tax strategy is a competitive advantage. Pros need QBI deduction calculation, passive activity loss (PAL) limitations, REPS qualification, and 1031 exchange tracking. Current finance/taxes.py handles depreciation + after-tax CF but stops there.

Acceptance Criteria

• Create core/services/tax_strategy.py with:
  • calculate_qbi_deduction(income, taxable_income, phase_out_threshold)
  • calculate_pal_limitation(passive_income, passive_losses, modified_agi)
  • check_reps_qualification(hours_worked, material_participation_tests)
  • track_1031_exchange(property_sold, property_acquired, timeline_days)
• Add TaxStrategy model linking to Property and Portfolio
• Add tax strategy view at /portfolio/tax-strategy/
• Show QBI deduction amount, PAL carryforward, and 1031 deadline countdown
• E2E test: navigate to tax strategy view, verify calculations render
• Unit tests for each tax calculation function

Implementation Guide (for opencode/mimo v2.5)

1. Create core/services/tax_strategy.py extending finance/taxes.py
2. Create TaxStrategy model in core/models/portfolio.py
3. Add tax strategy view at /portfolio/tax-strategy/
4. Show QBI deduction amount, PAL carryforward, and 1031 deadline countdown
5. E2E test: navigate to tax strategy view, verify calculations render
6. Unit tests for each tax calculation function

Dependencies

• Requires: Portfolio with InvestmentAnalysis data
• Related: Issue feat(portfolio): portfolio-level cash flow aggregation with blended DSCR #367 (portfolio cash flow aggregation)