feat: add native KDBX scaffolding and in-memory KeePass API

src/kdbx/header.ts

@@ -0,0 +1,24 @@
+import { BinaryReader } from "./binary";
+import type { KdbxHeader } from "./types";
+
+const KDBX_SIGNATURE_1 = 0x9aa2d903;
+const KDBX_SIGNATURE_2 = 0xb54bfb67;
+
+export function parseKdbxHeader(buffer: Uint8Array): { header: KdbxHeader; offset: number } {
+	const reader = new BinaryReader(buffer);
+	const signature1 = reader.readUint32LE();
+	const signature2 = reader.readUint32LE();
+
+	if (signature1 !== KDBX_SIGNATURE_1 || signature2 !== KDBX_SIGNATURE_2) {
+		throw new Error("Invalid KDBX signature");
+	}
+
+	const versionMinor = reader.readUint16LE();
+	const versionMajor = reader.readUint16LE();
+	const version = { major: versionMajor, minor: versionMinor };
+
+	return {
+		header: { version },
+		offset: buffer.length - reader.remaining(),
+	};
+}