Choose an Analytics & Monitoring Stack

Background: Native [platform] app, pre-launch. I want to understand
usage and catch crashes without drowning in tools or violating privacy.
Budget: [free-tier preferred / flexible].

Use case: Help me choose an analytics + crash/performance monitoring
stack and define exactly what to track.

Implementation details:
- Compare options for product analytics (e.g., Firebase Analytics,
  PostHog, Amplitude), crash reporting (Crashlytics, Sentry), and
  performance monitoring
- Privacy: what's collectable without consent, what needs App Tracking
  Transparency (iOS) / consent (Android), and minimizing PII
- Define a small, high-signal event taxonomy (don't track everything)
- A single analytics interface so I can swap vendors later

Layer & dependencies: Analytics calls go through one wrapper, not
sprinkled raw through views.

Deliverable: A recommended stack with reasoning, a starter event
taxonomy (event names + properties) tied to my key user flows, the
privacy/consent obligations per platform, and the wrapper-interface
design.