feat: add Store.redis() for standard Redis/ioredis/Valkey clients

[tenequm]

Adds Store.redis() - a new store adapter for standard Redis clients that handles BigInt-safe serialization internally.

Closes #208

Problem

Store.upstash() works because the Upstash REST SDK auto-serializes JSON (including BigInt) on their end. Standard Redis clients (ioredis, node-redis, Valkey) only accept strings, so passing channel state with BigInt fields directly to client.set() either throws or corrupts data.

Anyone running self-hosted Redis/Valkey has to write a custom store adapter with BigInt-safe serialization - which is error-prone and every self-hosted user rediscovers independently.

Solution

Store.redis() accepts any client with standard get/set/del string methods and handles serialization internally using ox's Json.parse/Json.stringify (same as Store.cloudflare() and Store.memory() already do):

import { Store } from 'mppx/server'
import Redis from 'ioredis'

const redis = new Redis('redis://localhost:6379')
const store = Store.redis(redis)

Interface

export function redis(client: redis.Parameters): Store

export declare namespace redis {
  type Parameters = {
    get: (key: string) => Promise<string | null>
    set: (key: string, value: string) => Promise<unknown>
    del: (key: string) => Promise<unknown>
  }
}

Works with ioredis, node-redis (@redis/client), Valkey, and any Redis-compatible client without requiring a specific package dependency.

Tests

• Added redis to the existing describe.each test matrix (roundtrip, missing key, delete, overwrite)
• Added redis json-roundtrips nested objects test
• Added redis roundtrips BigInt values test (the core issue this solves)

All 21 tests pass.