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>

scripts/test_openrouter.mjs

@@ -0,0 +1,36 @@
+import fs from "fs";
+import path from "path";
+
+const envContent = fs.readFileSync(".env.local", "utf-8");
+const apiKeyMatch = envContent.match(/OPENROUTER_API_KEY=([^\r\n]+)/);
+const apiKey = apiKeyMatch ? apiKeyMatch[1].trim() : "";
+
+console.log("Testing OpenRouter with key:", apiKey ? apiKey.substring(0, 15) + "..." : "NONE");
+
+async function testOpenRouter() {
+  // Test 1: List models or check deepseek/deepseek-v4-flash
+  const res = await fetch("https://openrouter.ai/api/v1/chat/completions", {
+    method: "POST",
+    headers: {
+      "Authorization": `Bearer ${apiKey}`,
+      "Content-Type": "application/json",
+      "HTTP-Referer": "http://localhost:3000",
+      "X-Title": "Receipt Scanner",
+    },
+    body: JSON.stringify({
+      model: "deepseek/deepseek-v4-flash",
+      messages: [
+        {
+          role: "user",
+          content: "Sag einfach 'Hallo, DeepSeek V4 Flash ist bereit!'"
+        }
+      ]
+    })
+  });
+
+  console.log("Status:", res.status, res.statusText);
+  const data = await res.json();
+  console.log("Response:", JSON.stringify(data, null, 2));
+}
+
+testOpenRouter().catch(console.error);