Replace KV storage with D1, add peer_id field, simplify README

Storage changes:
- Remove KV storage adapter
- Add D1 storage adapter for Cloudflare Workers
- Update schema to use peer_id instead of info field
- Add database migrations for D1

Documentation:
- Simplify README to be more concise
- Update deployment instructions for D1
- Add D1_SETUP.md explaining migration from KV
- Update DEPLOYMENT.md with D1 setup steps

API changes:
- Replace info field with peerId in session creation
- Update all storage interfaces and implementations

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

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

package.json

@@ -8,7 +8,8 @@
     "typecheck": "tsc",
     "dev": "ts-node src/index.ts",
     "start": "node dist/index.js",
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "deploy": "npm run build && npx wrangler deploy"
   },
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20251014.0",