Gracefully degrade homepage queue status during Redis outages

[roo-code-bruno]

Opened by @roo-code-bruno on behalf of Bruno Bergher. View the task or mention @roo-code-bruno for follow-up asks.

What problem this solves

HomeController#index was calling Sidekiq::Queue.new.size on every request, so Redis connection failures could raise before the homepage rendered.

Why this change was made

• move the queue lookup behind a narrow rescue path that treats Redis connectivity failures as unavailable queue status
• show the Redis card state explicitly so the page renders either the live queue count or an unavailable fallback
• cover both the healthy and Redis outage paths with controller tests

User impact

• the homepage keeps rendering when Redis is unavailable
• the Redis card shows Queue status unavailable instead of turning the whole request into a 500