refactor: simplify KPI to 4 metrics and update CLAUDE.md (#83)

KPI page: removed operational grid (Intäktstillväxt, Kostnadsandel,
Snittbetaltid — all usually empty or redundant). Now shows 4 cards
(Resultat, Kassa, Kundfordringar, Moms) + trend chart. Removed unused
fields from KPIReport type and simplified API route.

CLAUDE.md: documented MCP server extension, API key infrastructure,
OAuth 2.1 flow, gnubok-mcp npm package, KPI page, cookieless Supabase
client, and updated migration count (65 → 70).

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/api/reports/kpi/route.ts

@@ -4,13 +4,7 @@ import { generateIncomeStatement } from '@/lib/reports/income-statement'
 import { generateTrialBalance } from '@/lib/reports/trial-balance'
 import { generateARLedger } from '@/lib/reports/ar-ledger'
 import { generateMonthlyBreakdown } from '@/lib/reports/monthly-breakdown'
-import {
-  calculateGrossMargin,
-  calculateCashPosition,
-  calculateRevenueGrowth,
-  calculateExpenseRatio,
-  calculateAvgPaymentDays,
-} from '@/lib/reports/kpi'
+import { calculateCashPosition } from '@/lib/reports/kpi'
 import type { KPIReport } from '@/types'
 
 export async function GET(request: Request) {
@@ -24,7 +18,6 @@ export async function GET(request: Request) {
     return NextResponse.json({ error: 'period_id is required' }, { status: 400 })
   }
 
-  // Fetch fiscal period info
   const { data: period, error: periodError } = await supabase
     .from('fiscal_periods')
     .select('*')
@@ -36,31 +29,15 @@ export async function GET(request: Request) {
     return NextResponse.json({ error: 'Fiscal period not found' }, { status: 404 })
   }
 
-  // Run independent queries in parallel
-  const [
-    incomeStatement,
-    trialBalanceResult,
-    arLedger,
-    monthlyBreakdown,
-    paidInvoicesResult,
-  ] = await Promise.all([
-    generateIncomeStatement(supabase, user.id, periodId),
-    generateTrialBalance(supabase, user.id, periodId),
-    generateARLedger(supabase, user.id),
-    generateMonthlyBreakdown(supabase, user.id, periodId),
-    supabase
-      .from('invoices')
-      .select('invoice_date, paid_at')
-      .eq('user_id', user.id)
-      .eq('status', 'paid')
-      .not('paid_at', 'is', null)
-      .gte('invoice_date', period.period_start)
-      .lte('invoice_date', period.period_end),
-  ])
+  const [incomeStatement, trialBalanceResult, arLedger, monthlyBreakdown] =
+    await Promise.all([
+      generateIncomeStatement(supabase, user.id, periodId),
+      generateTrialBalance(supabase, user.id, periodId),
+      generateARLedger(supabase, user.id),
+      generateMonthlyBreakdown(supabase, user.id, periodId),
+    ])
 
-  const paidInvoices = (paidInvoicesResult.data || []) as { invoice_date: string; paid_at: string }[]
-
-  // Calculate VAT liability from trial balance (output VAT - input VAT)
+  // VAT liability from trial balance (output VAT - input VAT)
   const vatOutputAccounts = ['2611', '2621', '2631']
   const vatInputAccounts = ['2641', '2645']
   const outputVat = trialBalanceResult.rows
@@ -69,33 +46,13 @@ export async function GET(request: Request) {
   const inputVat = trialBalanceResult.rows
     .filter((r) => vatInputAccounts.includes(r.account_number))
     .reduce((sum, r) => sum + (r.closing_debit - r.closing_credit), 0)
-  const vatLiability = Math.round((outputVat - inputVat) * 100) / 100
-
-  // Revenue growth: only for closed periods, compare with previous period
-  let revenueGrowth: number | null = null
-  if (period.is_closed && period.previous_period_id) {
-    const prevStatement = await generateIncomeStatement(
-      supabase,
-      user.id,
-      period.previous_period_id
-    )
-    revenueGrowth = calculateRevenueGrowth(
-      incomeStatement.total_revenue,
-      prevStatement.total_revenue
-    )
-  }
 
   const report: KPIReport = {
-    grossMargin: calculateGrossMargin(incomeStatement),
     netResult: incomeStatement.net_result,
     cashPosition: calculateCashPosition(trialBalanceResult.rows),
     outstandingReceivables: arLedger.total_outstanding,
     overdueReceivables: arLedger.total_overdue,
-    revenueGrowth,
-    expenseRatio: calculateExpenseRatio(incomeStatement),
-    avgPaymentDays: calculateAvgPaymentDays(paidInvoices),
-    paidInvoiceCount: paidInvoices.length,
-    vatLiability,
+    vatLiability: Math.round((outputVat - inputVat) * 100) / 100,
     totalRevenue: incomeStatement.total_revenue,
     totalExpenses: incomeStatement.total_expenses,
     periodComplete: period.is_closed,