fix: add hSetNX to Redis transaction interface

[mvanhorn]

Summary

Adds hSetNX to the Redis transaction interface (TxClientLike) and both transaction class implementations. The method exists in the non-transaction RedisClient but was missing from transactions.

Why this matters

#184 reports that hSetNX is unavailable in transactions. The TxClientLike type has hSet, hGet, hMGet, hGetAll, hDel, hScan, hKeys, hIncrBy, and hLen but not hSetNX. This makes it impossible to use atomic hash-set-if-not-exists operations within Redis transactions.

Changes

• packages/redis/src/types/redis.ts - Added hSetNX to TxClientLike type
• packages/redis/src/RedisClient.ts - Added hSetNX to the transaction class, following the same pattern as hSet (queue with transactionId, return this)
• packages/public-api/src/apis/redis/RedisClient.ts - Added hSetNX and lowercase hsetnx alias to the public-api transaction class, matching the alias pattern used by hset/hSet, hincrby/hIncrBy, etc.

Testing

The implementation follows the exact pattern of existing hash methods in the transaction classes. No new test infrastructure was needed - the method signature and behavior matches the non-transaction hSetNX (queuing the command with transactionId instead of scope).

Fixes #184

This contribution was developed with AI assistance (Claude Code + Codex CLI).

[stephenoid]

@mvanhorn, would you please sign our contributor agreement?

[mvanhorn]

Signed the CLA.

[niedzielski]

thanks! i'll try to merge this monday.