Add tax features: summary report, deductible expenses, invoice tax fix, CSV export

- Add taxDeductible boolean to expenses schema + migration 0002
- Update expenses router, form, and list to support tax-deductible flag
- Fix invoice-view tax calculation (was hardcoded $0.00; now uses taxRate)
- New Tax Summary tab in Reports: year selector, income/deductions breakdown,
  SE tax + federal income estimates, quarterly bar chart
- CSV export for accountant with income + expense rows and tax summary

https://claude.ai/code/session_012sqEgNQpx676isepeoX4Mi

drizzle/0002_tax_deductible.sql

@@ -0,0 +1 @@
+ALTER TABLE "beenvoice_expense" ADD COLUMN "taxDeductible" boolean DEFAULT false NOT NULL;