Add relay server for remote HTTPS access

Node.js/TypeScript relay server that enables remote access to MacroPad:
- WebSocket-based communication between desktop and relay
- Password authentication with bcrypt hashing
- Session management with consistent IDs
- REST API proxying to desktop app
- Web client WebSocket relay
- Login page and PWA-ready app page
- Designed for cloud-node-container deployment

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

macropad-relay/src/utils/idGenerator.ts

@@ -0,0 +1,31 @@
+// Unique ID generation utilities
+
+import { randomBytes } from 'crypto';
+
+const BASE62_CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+
+/**
+ * Generate a random base62 string of specified length.
+ * Uses cryptographically secure random bytes.
+ */
+export function generateSessionId(length: number = 6): string {
+  const bytes = randomBytes(length);
+  let result = '';
+
+  for (let i = 0; i < length; i++) {
+    result += BASE62_CHARS[bytes[i] % BASE62_CHARS.length];
+  }
+
+  return result;
+}
+
+/**
+ * Generate a UUID v4 for request IDs.
+ */
+export function generateRequestId(): string {
+  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
+    const r = Math.random() * 16 | 0;
+    const v = c === 'x' ? r : (r & 0x3 | 0x8);
+    return v.toString(16);
+  });
+}