Migrate redis from v3 to v6

[Nikoklis]

Replaces #490. That bump cannot be merged as-is: node-redis v4 rewrote the client API and the build fails. This PR does the actual migration.

Before / after

Client usage (breaking for orka consumers):

// before (v3, callbacks)
getRedis().get('key', (err, value) => { ... });

// after (v6, promises)
const value = await getRedis().get('key');

config.redis schema: unchanged. url, options.tls and the legacy retry/keepalive options (timesConnected, totalRetryTime, reconnectAfterMultiplier, socketKeepalive, socketInitialDelay) keep working and are mapped to the new driver options. Any other key in config.redis.options (e.g. RESP, pingInterval, socket) is passed through to createClient.

Initializer internals:

	before (v3)	after (v6)
Client creation	createClient(url, options)	createClient({ url, RESP: 2, socket })
Connection	implicit	explicit client.connect(), awaited during boot; if redis is down the app still boots and /health reports unhealthy
Reconnect	retry_strategy	socket.reconnectStrategy, same semantics
Too many reconnects	thrown error crashed the process	stops reconnecting; /health turns 503 so the orchestrator restarts the pod
Health check	client.connected	client.isReady
Keep-alive	manual setKeepAlive on client.stream	socket.keepAlive / socket.keepAliveInitialDelay
Close (tests)	client.end(true)	client.destroy()
Types	@types/redis	shipped with the driver (@types/redis removed)

RESP is pinned to 2 to preserve reply shapes; set config.redis.options.RESP = 3 to opt in to RESP3.

Breaking changes

• getRedis() returns a promise-based node-redis v6 client; callback-style commands and client.end() are gone.
• createRedisConnection() is now async and resolves after the initial connection attempt.
• node-redis v6 requires Node >= 20 (CI matrix already is 20/22/24).
• Requires a major orka release.

Testing

• Unit tests rewritten for the new API (option mapping, TLS, all reconnect-strategy branches).
• Redis example e2e passes against a real redis: connect, /health 200, destroy(), /health 503.
• Manual smoke test of set/get/del through getRedis().

🤖 Generated with Claude Code

[klesgidis]

LGTM! maybe we should give it a try before releasing this

[Nikoklis]

Will merge and get a new rc tag from master and test it.