feat: M5 Prekey Server + M7 Wire Format

M5: Shade Prekey Server (Hono)
- REST API: register, fetch bundle, replenish, count, delete
- MemoryPrekeyStore for testing/embedded use
- Standalone Docker deployment (Dockerfile + standalone.ts)
- One-time prekey consumption on bundle fetch

M7: Compact binary wire format
- Version-tagged envelopes (PreKeyMessage, RatchetMessage)
- Length-prefixed byte arrays, big-endian integers
- Significantly smaller than JSON (no base64 bloat)
- Roundtrip encode/decode for all message types

100 tests, 0 failures across M1-M5+M7.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shade-server/src/index.ts

@@ -0,0 +1,28 @@
+import { Hono } from 'hono';
+import { createPrekeyRoutes } from './routes.js';
+import { MemoryPrekeyStore } from './memory-store.js';
+import type { PrekeyStore } from './store.js';
+
+export { createPrekeyRoutes } from './routes.js';
+export { MemoryPrekeyStore } from './memory-store.js';
+export type { PrekeyStore } from './store.js';
+
+/**
+ * Create a standalone Shade Prekey Server.
+ *
+ * Can be used standalone (Docker) or embedded in another Hono app.
+ *
+ * Standalone:
+ *   const server = createPrekeyServer();
+ *   export default { port: 3900, fetch: server.fetch };
+ *
+ * Embedded:
+ *   const app = new Hono();
+ *   app.route('/shade', createPrekeyServer());
+ */
+export function createPrekeyServer(options?: {
+  store?: PrekeyStore;
+}): Hono {
+  const store = options?.store ?? new MemoryPrekeyStore();
+  return createPrekeyRoutes(store);
+}