Split the README into docs/ pages, add web UI screenshots

- README is the overview; web UI, pages, Home Assistant, how it works,
  wiring, Nano over WiFi and the recovery app have their own page in docs/.
- docs/web-ui.md has a screenshot of every tab, made with headless Edge by
  tools/make_webui_screenshots.py.
- The web UI opens a page in the editor with #pages/<name>. Version 2.7.2.
- The reply wire is fitted (flashing the Nano over WiFi works).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/pages.md

@@ -0,0 +1,22 @@
+# Pages
+
+[← Back to the README](../README.md)
+
+The dynamic pages on the display, drawn by the ESP32 itself (`python
+tools/make_page_screenshots.py` makes these pictures again). The Clock page is built in;
+the others are the example pages in [examples/home-pages.json](../examples/home-pages.json)
+(import them in the web UI, System tab; they use this home's Home Assistant entities).
+
+| Page | |
+|---|---|
+| **Clock** (built in), day and from 17:00 | ![Clock](../Pictures/pages/clock-0000.png) ![Clock, evening](../Pictures/pages/clock-1700.png) |
+| **Weer**: clock, weather icon by state, humidity, temperature | ![Weer](../Pictures/pages/weer.png) |
+| **Dag en nacht**: sun from 07:00, moon and stars from 19:00, date | ![Dag en nacht, day](../Pictures/pages/dag-en-nacht-0700.png) ![Dag en nacht, night](../Pictures/pages/dag-en-nacht-1900.png) |
+| **Energie**: net power now, solar today, clock | ![Energie](../Pictures/pages/energie.png) |
+| **3D printer**: progress, time left, status message (scrolls), nozzle temperature | ![3D printer](../Pictures/pages/3d-printer.png) |
+| **Binnen**: room and outside temperature, CO2, air quality | ![Binnen](../Pictures/pages/binnen.png) |
+| **Verbruik**: water and energy used today, solar today | ![Verbruik](../Pictures/pages/verbruik.png) |
+| **Grote klok**: big clock, inverted from 22:00 | ![Grote klok](../Pictures/pages/grote-klok-0700.png) ![Grote klok, night](../Pictures/pages/grote-klok-2200.png) |
+| **Datum**: weekday and date | ![Datum](../Pictures/pages/datum.png) |
+| **Aftellen**: countdown to Christmas | ![Aftellen](../Pictures/pages/aftellen.png) |
+| **Stopwatch** | ![Stopwatch](../Pictures/pages/stopwatch.png) |