Release v0.1.34: Low-Balance Credit Warning

What changed

The sidebar credit balance widget now proactively warns users when their balance drops below 500 credits (£5.00). When triggered, the component:

• Switches to an amber visual state with an alert icon
• Shows a tooltip: "Low balance — top up to keep pipelines running"
• Fires a one-time session toast with a "Top Up" button linking to billing settings

Why it matters

Users can now see at a glance when they're running low and top up before a pipeline run fails mid-execution. The one-time toast ensures the warning isn't repetitive noise across re-renders or refetch ticks.

Technical notes

Threshold is 500 credits (£5.00) — roughly 3–6 more runs at current pricing. Session-guard logic uses useRef to fire the toast only once per session, not on every balance check.