Phase 6: Expand market rates and enhance AI investment recommendations

- Rate fetcher now scrapes CD, Money Market, and High Yield Savings rates
  from Bankrate.com with pauses between fetches to avoid rate limiting
- Historical rate data is preserved (no longer deleted on each fetch)
- Database migration adds rate_type column and tenant ai_recommendations table
- Backend returns market rates grouped by type with latest-batch-only queries
- AI prompt now includes all three rate types for comprehensive analysis
- AI recommendations are saved per-tenant for retrieval on page load
- Frontend: "Market CD Rates" replaced with "Today's Market Rates" tabbed view
- Rates section is collapsible (expanded by default) to save screen space
- Saved recommendations load automatically with "Last Updated" timestamp

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

backend/src/database/tenant-schema.service.ts

@@ -316,6 +316,17 @@ export class TenantSchemaService {
         updated_at TIMESTAMPTZ DEFAULT NOW()
       )`,
 
+      // AI Investment Recommendations (saved per tenant)
+      `CREATE TABLE "${s}".ai_recommendations (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        recommendations_json JSONB NOT NULL,
+        overall_assessment TEXT,
+        risk_notes JSONB,
+        requested_by UUID,
+        response_time_ms INTEGER,
+        created_at TIMESTAMPTZ DEFAULT NOW()
+      )`,
+
       // Attachments (file storage for receipts/invoices)
       `CREATE TABLE "${s}".attachments (
         id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),