fix: enforce Redis TLS certificate verification for rate limiter

[winhowes]

Motivation

• Close a security regression where rediss:// connections disabled certificate validation via InsecureSkipVerify, allowing on‑path attackers to impersonate Redis and capture AUTH credentials or tamper with rate limiting state.
• Ensure operators who opt into TLS get authentic server verification by default.

Description

• Removed the fallback that set tls.Config.InsecureSkipVerify = true when --redis-ca was not provided so TLS connections perform normal certificate verification by default in both allowRedis and retryAfterRedis.
• Updated the --redis-ca flag description (removed the wording implying it "disables InsecureSkipVerify").
• Modified the existing tests in app/redis_tls_auth_test.go to assert that rediss:// with an untrusted certificate fails verification unless a CA is provided, and renamed the test to TestRateLimiterRedisTLSAuthRequiresVerification.

Testing

• Ran the package test suite with go test ./app and all tests passed.
• The modified TLS verification tests exercise both failure without a CA and success when a CA is supplied (existing tests cover the latter), validating the behavior change.

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Codex Task

[winhowes]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 1365aaf460

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[winhowes]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

ℹ️ About Codex in GitHub

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