feat: Finanzplan Phase 1-4 — DB + Engine + API + Spreadsheet-UI

Phase 1: DB-Schema (12 fp_* Tabellen) + Excel-Import (332 Zeilen importiert)
Phase 2: Compute Engine (Personal, Invest, Umsatz, Material, Betrieblich, Liquiditaet, GuV)
Phase 3: API (/api/finanzplan/ — GET sheets, PUT cells, POST compute)
Phase 4: Spreadsheet-UI (FinanzplanSlide als Annex mit Tab-Leiste, editierbarem Grid, Jahres-Navigation)

Zusaetzlich:
- Gruendungsdatum verschoben: Feb→Aug 2026 (DB + Personalkosten)
- Neue Preisstaffel: Startup/<10 MA ab 3.600 EUR/Jahr (14-Tage-Test, Kreditkarte)
- Competition-Slide: Pricing-Tiers aktualisiert

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

pitch-deck/app/api/finanzplan/compute/route.ts

@@ -0,0 +1,38 @@
+import { NextRequest, NextResponse } from 'next/server'
+import pool from '@/lib/db'
+import { computeFinanzplan } from '@/lib/finanzplan/engine'
+
+export async function POST(request: NextRequest) {
+  try {
+    const body = await request.json().catch(() => ({}))
+    const scenarioId = body.scenarioId
+
+    // Get scenario ID
+    let sid = scenarioId
+    if (!sid) {
+      const { rows } = await pool.query('SELECT id FROM fp_scenarios WHERE is_default = true LIMIT 1')
+      if (rows.length === 0) {
+        return NextResponse.json({ error: 'No default scenario found' }, { status: 404 })
+      }
+      sid = rows[0].id
+    }
+
+    const result = await computeFinanzplan(pool, sid)
+
+    return NextResponse.json({
+      scenarioId: sid,
+      computed: true,
+      summary: {
+        total_revenue_y2026: result.umsatzerloese.total.m1 !== undefined
+          ? Object.values(result.umsatzerloese.total).reduce((a, b) => a + b, 0)
+          : 0,
+        total_costs_y2026: Object.values(result.betriebliche.total_gesamt).reduce((a, b) => a + b, 0),
+        headcount_m60: result.personalkosten.headcount.m60 || 0,
+        cash_balance_m60: result.liquiditaet.endstand.m60 || 0,
+      },
+    })
+  } catch (error) {
+    console.error('Finanzplan compute error:', error)
+    return NextResponse.json({ error: String(error) }, { status: 500 })
+  }
+}