feat(mobile): enable PostHog error tracking and user identification

[Gilbert09]

Problem

The mobile app captured screen views, touches, and session replays, but two gaps meant that data was hard to act on:

• No error tracking — uncaught JS exceptions and unhandled promise rejections were never sent to PostHog, so crashes were invisible in Error Tracking.
• No user identification — every event and session replay was anonymous, so we couldn't attribute behaviour to a person, org, or staff/non-staff.

Changes

• Error tracking (src/lib/posthog.ts): added an errorTracking.autocapture config to POSTHOG_OPTIONS enabling uncaughtExceptions and unhandledRejections.
• User identification (src/lib/posthog.ts): new useIdentifyUser() hook that identifies the signed-in user (uuid as distinct id, with email / name / is_staff properties and an organization group) once their profile loads, and calls posthog.reset() on logout so sessions don't bleed across accounts.
• Wired useIdentifyUser() into RootLayoutNav in src/app/_layout.tsx alongside the existing useScreenTracking().

How did you test this?

• tsc --noEmit — no new type errors introduced by the changed files.
• biome check on both changed files — clean.
• Verified the errorTracking and identify/reset/group APIs against the installed posthog-react-native v4.18.0 type definitions.

Not manually exercised on a device/simulator.

Publish to changelog?

no

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 1
apps/mobile/src/lib/posthog.ts:79-93
**Stale user properties and missing group after initial identification**

The `identifiedUuid.current === user.uuid` guard correctly prevents spamming `posthog.identify()` on every render, but it also means that any mid-session property changes — a user gaining staff access, updating their email, or being assigned to an organization for the first time — are never forwarded to PostHog until the user logs out and back in. The `posthog.group()` call is particularly affected: if `user.organization` is `null` at identification time and the user joins an org later in the same session, the group association is never sent.

_{Reviews (1): Last reviewed commit: "feat(mobile): enable PostHog error track..." | Re-trigger Greptile}

[github-actions]

No showstoppers. The hook is well-guarded, the stale-identity concern raised by the bot was addressed in the current diff (JSON signature over the full payload), and error tracking config is a safe additive option.

New commits pushed (delta classified non_trivial_delta) — stamphog approval dismissed; re-review running automatically.

[github-actions]

Additive mobile analytics change with no showstoppers. The hook is well-guarded, the stale-identity concern raised in review was addressed in the current diff via JSON signature over the full payload, and error tracking config is a safe opt-in option.