LAUNCH BLOCKER: Supabase Realtime drops connections on free plan

## Launch Blocker Report

### Feature Affected
Real-time build status alerts (core feature)

### Problem
On the Supabase free plan, Realtime connections are capped at 200 concurrent. During testing with 3 simulated clients, we observed:
- Connections dropping after ~8 minutes idle
- 3-5 second delay on alert delivery (should be <1s)
- Occasional "channel closed" errors with no client-side recovery

### Why This Is A Blocker
VCTRL's primary value is: "Know the moment your build breaks."
If alerts arrive 5 seconds late or not at all, the core promise is broken.

### Options

**Option A: Upgrade Supabase to Pro ($25/mo)**
- Removes connection limits
- 500ms or better latency
- Straightforward fix
- Cost acceptable for launch infrastructure

**Option B: Self-manage Realtime with Ably or Pusher**
- More control
- Additional vendor dependency
- Overkill for V1

**Option C: Polling fallback**
- 2-second poll as fallback when Realtime drops
- Can ship faster, graceful degradation
- Not ideal but acceptable for beta

### Decision
Upgrade to Supabase Pro before launch. Implement Option C (poll fallback) as belt-and-suspenders.

### Status
Blocking launch. Supabase Pro upgrade pending billing setup.

### Owner
@dom — handle before EOW.