feat(shared): cross-cutting plumbing and pure domain layer

Typed pydantic-settings config, structlog JSON logging with request/trace id
propagation and redaction of phone numbers, tokens and face keys, the unified
response envelope and error-code table from 架构文档 §9.2, async SQLAlchemy
session management, ORM models for the eight foundation tables, and the
OpenTelemetry/Prometheus wiring.

packages/domain stays pure logic -- snowflake ids, the quota three-phase
protocol and the tk_task state machine -- so it can be tested without a
database and is held to mypy strict.

packages/shared/redis_client.py

@@ -0,0 +1,28 @@
+"""Shared Redis connection (cache / quota counters / cost budget counter)."""
+
+from __future__ import annotations
+
+from redis.asyncio import Redis, from_url
+
+from packages.shared.config import Settings, get_settings
+
+_client: Redis | None = None
+
+
+def create_redis(settings: Settings | None = None) -> Redis:
+    cfg = settings or get_settings()
+    return from_url(cfg.redis_url, encoding="utf-8", decode_responses=True)
+
+
+def get_redis() -> Redis:
+    global _client
+    if _client is None:
+        _client = create_redis()
+    return _client
+
+
+async def close_redis() -> None:
+    global _client
+    if _client is not None:
+        await _client.aclose()
+    _client = None