Add full application: receipt scanning, auth, billing, and account deletion

Brings the working codebase (Next.js app, auth system, Stripe billing,
Docker/deploy config, tests, docs) into version control on top of the
placeholder initial commit, and adds account self-deletion (Danger Zone
in Settings, password + typed-email confirmation, cascading DB cleanup,
Stripe cancellation) per GDPR right-to-erasure.

Excludes local build caches, node_modules, and internal agent scratch
files; .gitignore hardened to keep those out going forward.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test_pipeline.mjs

@@ -0,0 +1,67 @@
+import fs from "fs";
+import path from "path";
+import { generateDualSheetExcel } from "./src/lib/export/excelGenerator.ts";
+import { generateDatevCsv } from "./src/lib/export/csvGenerator.ts";
+import { validateReceiptMath } from "./src/lib/ai/mathValidator.ts";
+import { generateDeterministicDemoExtraction } from "./src/lib/ai/extractor.ts";
+
+async function testPipeline() {
+  console.log("=== 🧾 TESTING RECEIPT SCANNER PIPELINE ===");
+
+  // 1. Test Demo Extraction
+  const sample1 = generateDeterministicDemoExtraction("Aral_Tankstelle.jpg");
+  console.log("✓ Sample Extraction Generated:", sample1.merchant.name, "Total:", sample1.totalAmount.value);
+
+  // 2. Test Math Validation
+  const mathValid = validateReceiptMath(sample1);
+  console.log("✓ Math Validation Result (Valid case):", mathValid.isMathValid ? "VALID ✓" : "INVALID ✗");
+
+  // Inconsistent case test
+  const brokenSample = {
+    ...sample1,
+    totalAmount: { value: 100.0, confidence: 0.99 },
+    netAmount: 50.0,
+    taxBreakdown: [{ ratePercent: 19, taxAmount: 9.5, netAmount: 50.0 }],
+  };
+  const mathInvalid = validateReceiptMath(brokenSample);
+  console.log("✓ Math Validation Discrepancy Detection (Discrepant case):", !mathInvalid.isMathValid ? "DETECTED AS EXPECTED ✓" : "FAILED ✗");
+
+  // 3. Test Dual Sheet Excel Generation
+  const testReceipts = [
+    {
+      ...sample1,
+      id: "rcpt_test_1",
+      imageHash: "hash_test_1",
+      originalFileName: "Aral_Tankstelle.jpg",
+      fileSizeBytes: 102400,
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+      status: "ready",
+    },
+    {
+      ...generateDeterministicDemoExtraction("Trattoria_Bella_Vista.jpg"),
+      id: "rcpt_test_2",
+      imageHash: "hash_test_2",
+      originalFileName: "Trattoria_Bella_Vista.jpg",
+      fileSizeBytes: 204800,
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+      status: "ready",
+    }
+  ];
+
+  const excelBuffer = await generateDualSheetExcel(testReceipts);
+  console.log("✓ Dual-Sheet Excel (.xlsx) generated successfully. Size:", excelBuffer.length, "bytes");
+
+  // 4. Test DATEV CSV Generation
+  const datevCsv = generateDatevCsv(testReceipts);
+  console.log("✓ DATEV CSV generated successfully. Starts with UTF-8 BOM:", datevCsv.startsWith("\uFEFF") ? "YES ✓" : "NO ✗");
+  console.log("✓ Semicolon delimited count:", (datevCsv.match(/;/g) || []).length);
+
+  console.log("=== ALL CORE PIPELINE TESTS PASSED SUCCESSFULLY! ===");
+}
+
+testPipeline().catch(err => {
+  console.error("Test failed:", err);
+  process.exit(1);
+});