Server side:
- POST /api/v1/billing/usage/increment endpoint with dimension whitelist
(hand_executions, pipeline_runs, relay_requests) and count validation (1-100)
- Returns updated usage quota after increment
Desktop side:
- New saas-billing.ts mixin with incrementUsageDimension() and
reportUsageFireAndForget() (non-blocking, safe for finally blocks)
- handStore.triggerHand: reports hand_executions after successful run
- PipelinesPanel.handleRunComplete: reports pipeline_runs on completion
- SaaSClient type declarations for new billing methods
Billing pipeline now covers all three dimensions:
relay_requests → relay handler (server-side, real-time)
hand_executions → handStore (client-side, fire-and-forget)
pipeline_runs → PipelinesPanel (client-side, fire-and-forget)
