multi-tenant Phase 1: user registry + per-user memory

- CDK: add agent-claw-users DynamoDB table (actor_id PK, RETAIN policy)
- CDK: grant agent-runner read/write on users table; add USERS_TABLE_NAME env
- CDK: fix cdk.json app field (was object, must be command string)
- CDK: add UsersTableName output
- agent-runner: get_or_create_user() auto-registers users on first contact
  (stores display_name, telegram_username, created_at, allowed)
- agent-runner: pass user_profile in AgentCore payload
- prompt_builder: split base prompt (cached) from per-user context (injected per-call)
  removes USER.md/MEMORY.md from shared load; user name/username injected dynamically
- main.py: extract user_profile from payload, build user_context string for prompt

cdk/cdk.json

@@ -1,7 +1,5 @@
 {
-  "app": {
-    "outdir": "cdk.out"
-  },
+  "app": "npx ts-node --prefer-ts-exts bin/agent-claw.ts",
   "context": {
     "@aws-cdk/aws-apigateway:usagePlanKeyOrderInsensitiveId": true,
     "@aws-cdk/core:stackRelativeExports": true