ui(redis): surface TYPE/TTL batch failure on keys view

[ZhuchkaTriplesix]

Parent

Part of #445

Severity

Medium

Problem

typesAndTtls failure falls back to type: 'unknown' / ttl: -1 with no banner. Keys look loaded but type/TTL are wrong.

Evidence

• lib/features/redis/redis_keys_view.dart (~83–97)
• Existing _buildErrorBanner path for other errors

Acceptance

• Pipeline/metadata failure shows non-blocking error banner (or per-row unavailable state)
• Keys list still usable
• Successful path unchanged

Suggested fix

Catch batch failure → set _error / banner; keep key names from SCAN.

[ZhuchkaTriplesix]

Shipped on dev via #462 (Closes did not auto-close because PRs targeted dev).