XP display as entry point to a personal statistics view

## Idea

The XP total displayed in the top-right corner of the app should be clickable and lead to a personal statistics screen. Right now that number is a dead end — tapping it should take you somewhere meaningful.

The statistics view doesn't need to be exhaustive. Some directions that feel natural:

- **XP over time** — a chart showing earned XP by day/week/month
- **Per-chore breakdown** — how often each chore has been completed and how much XP it has contributed in total
- A combination of both on a single screen

The exact content is open; the core request is that the XP display becomes a navigation entry point rather than purely decorative.

## Relationship to existing issues

- Overlaps with #9 (F07 — Graphical XP overview), which covers a broader widget-based stats screen. This idea specifically anchors the entry point in the XP chip and keeps the scope minimal.

## Open questions

- Should clicking the XP chip open a dedicated stats page, or a quick-view panel/drawer?
- Is per-chore breakdown part of the first iteration, or a follow-up?