Add Redis support

[mfauzaan]

Summary

• add redis:// and rediss:// connections with optional password/ACL authentication, logical database selection, Keychain-backed credentials, and Redis/Valkey Docker discovery
• add a binary-safe Redis driver using valkey-swift 1.5.0, a bounded cursor-based key browser, type-aware value inspection/editing, TTL/rename/delete operations, and a dedicated command workspace
• add command confirmation, pooled-connection safety rules, credential-aware history redaction, capability gates for non-relational UI, Redis assets, documentation, and focused unit/live tests

Library choice

This pins valkey-swift 1.5.0. It is the maintained Swift 6, structured-concurrency Redis/Valkey client that fits Pluk's existing SwiftNIO and actor boundaries. The release also includes command-cancellation and connection-close fixes relevant to a long-lived desktop client.

The client uses RESP3, so Pluk requires Redis 6.0+ or a compatible Valkey server. Upstream guarantees Redis compatibility through 7.2.4; newer releases may work but are documented as requiring validation.

Safety and performance

• key discovery uses bounded SCAN pages only; no production path sends KEYS
• keys, values, and unsigned 64-bit cursors remain binary/representation safe
• destructive writes require explicit confirmation, while commands that can monopolize or poison pooled connections are denied
• authentication/configuration secrets are excluded or redacted before history persistence, and sanitized commands cannot be replayed
• rediss:// performs normal certificate and hostname verification

Verification

• full hosted PlukTests suite passed
• macOS Release build passed, and the exact built binary was launched to verify the Redis connection UI
• Redis 7.2.6 live matrix passed for plain, password-only, and ACL authentication, reconnect behavior, DB 0/1 isolation, core data structures, TTLs, and command execution
• 101,000-key mixed dataset completed a deliberately small-COUNT traversal in 10.785s (11.075s repeat), with 42,360 SCAN calls and exactly zero KEYS calls
• self-signed TLS was correctly rejected by Pluk's normal trust validation

Known MVP limitations are documented: no Cluster, Sentinel, or Redis-over-SSH support; RedisJSON is optional; streams are read-only and bounded to their first page.

Closes #139