Prevent cold-start bootstrap stampede with single-flight request locking

[Copilot]

Description

Cold-start requests were executing full bootstrap work (migrations, collection/form sync, plugin bootstrap) in request middleware, and concurrent cold-start traffic could duplicate that work before the completion flag flipped. This change serializes bootstrap execution per worker instance so concurrent requests await one in-flight bootstrap instead of stampeding.

Changes

• Bootstrap concurrency control
  • Added a module-level in-flight promise lock in bootstrap.ts.
  • First request creates and runs bootstrap; concurrent requests await the same promise.
  • Lock is cleared in finally; successful bootstrap still sets bootstrapComplete = true.
• Bootstrap reset behavior
  • resetBootstrap() now resets both completion and in-flight state for deterministic test isolation.
• Regression coverage for cold-start concurrency
  • Added a deterministic concurrent-request unit test that proves heavy bootstrap services are invoked once under overlap.
  • Added/updated mocks to include form-collection sync in concurrency assertions.

if (!bootstrapInFlight) {
  bootstrapInFlight = (async () => {
    try {
      // migrations + sync + plugin bootstrap
      bootstrapComplete = true
    } finally {
      bootstrapInFlight = null
    }
  })()
}
await bootstrapInFlight

Testing

Unit Tests

• Added/updated unit tests
• All unit tests passing

E2E Tests

• Added/updated E2E tests
• All E2E tests passing

Screenshots/Videos

N/A (no UI changes)

Checklist

• Code follows project conventions
• Tests added/updated and passing
• Type checking passes
• No console errors or warnings
• Documentation updated (if needed)

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