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-proto/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src"
+  },
+  "include": ["src"]
+}