[codex] Add PostHog error tracking

[willwearing]

What changed

• Enables PostHog exception capture in the web client and switches manual frontend error capture to captureException.
• Adds Next.js app-router error boundaries plus onRequestError server capture for request-time errors.
• Switches the Nest backend helper to PostHog's SDK captureException path with request context.
• Wires PostHog source map upload for production web builds when the upload env vars are present.
• Documents the required PostHog env vars and adds focused tests around the backend helper and frontend error helper.

Validation

• apps/web: bun x vitest run src/lib/posthog/tests/events.test.ts
• apps/web: bun x tsc --noEmit
• apps/web: bun run build
• backend: bun run test -- posthog.service.spec.ts
• packages/shared: bun x tsc
• backend: bun run build

Note: the first backend direct tsc attempt failed before @graspful/shared had been built locally. Building packages/shared first fixed that workspace-order issue.

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Project	Deployment	Actions	Updated (UTC)
graspful	Ready	Preview, Comment	May 5, 2026 5:01pm