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/route.ts

@@ -0,0 +1,32 @@
+import { NextResponse } from 'next/server'
+import pool from '@/lib/db'
+import { SHEET_LIST } from '@/lib/finanzplan/types'
+
+export async function GET() {
+  try {
+    const scenarios = await pool.query('SELECT * FROM fp_scenarios ORDER BY is_default DESC, name')
+
+    // Get row counts per sheet
+    const sheets = await Promise.all(
+      SHEET_LIST.map(async (s) => {
+        const tableName = `fp_${s.name}`
+        try {
+          const { rows } = await pool.query(
+            `SELECT COUNT(*) as total, COUNT(*) FILTER (WHERE is_editable = true) as editable FROM ${tableName} WHERE scenario_id = (SELECT id FROM fp_scenarios WHERE is_default = true LIMIT 1)`
+          )
+          return { ...s, rows: parseInt(rows[0]?.total || '0'), editable_rows: parseInt(rows[0]?.editable || '0') }
+        } catch {
+          return s
+        }
+      })
+    )
+
+    return NextResponse.json({
+      sheets,
+      scenarios: scenarios.rows,
+      months: { start: '2026-01', end: '2030-12', count: 60, founding: '2026-08' },
+    })
+  } catch (error) {
+    return NextResponse.json({ error: String(error) }, { status: 500 })
+  }
+}