Bug & tweak sprint: fix financial calculations, add quarterly report, enhance dashboard

- Fix Accounts page: include investment accounts in Est. Monthly Interest calc,
  add Fund column to investment table, split summary cards into Operating/Reserve
- Fix Cash Flow: ending balance now respects includeInvestments toggle
- Fix Budget Manager: separate operating/reserve income in summary cards
- Fix Projects: default sort by planned_date instead of name
- Add Vendors: last_negotiated date field with migration, CSV import/export
- New Quarterly Financial Report: budget vs actuals, over-budget flagging, YTD
- Enhance Dashboard: separate Operating/Reserve fund cards, expanded Quick Stats
  with monthly interest, YTD interest earned, planned capital spend

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

db/migrations/008-vendor-last-negotiated.sql

@@ -0,0 +1,16 @@
+-- Migration: Add last_negotiated date to vendors table
+-- Bug & Tweak Sprint
+
+DO $$
+DECLARE
+  tenant_schema TEXT;
+BEGIN
+  FOR tenant_schema IN
+    SELECT schema_name FROM shared.organizations WHERE schema_name IS NOT NULL
+  LOOP
+    EXECUTE format(
+      'ALTER TABLE %I.vendors ADD COLUMN IF NOT EXISTS last_negotiated DATE',
+      tenant_schema
+    );
+  END LOOP;
+END $$;