Show status messages on the display

- Clock firmware: 'Connecting to WiFi...' and 'Getting the time...' at
  boot, 'Crashed!' in the OTA-only modes, and 'No WiFi' with the time
  when WiFi is down for over a minute (new DisplayController screen)
- Recovery app: shows its reason, the setup WiFi name, or its IP address,
  then powers the display off (flipdots keep the image)
- StatusScreen and drawTextLines shared by both apps
- Driver: ESP begin() no longer draws 'ESP Connected'
- Tests: No WiFi screen, short reason texts (70 total)

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

README.md

@@ -163,7 +163,8 @@ even if the uploader is interrupted.
 The ESP32 has a small second app, the **recovery app** ([src/recovery](src/recovery)). It
 has its own place on the flash and is never changed by OTA updates. It contains only WiFi,
 a setup web page and OTA, so the ESP32 can always be reached, even when the clock firmware
-is broken. The display stays off while it runs, and the built-in LED double-blinks.
+is broken. It shows what is going on as a short message on the display, and the built-in
+LED double-blinks.
 
 ```
 flash (4 MB):  bootloader | nvs | otadata | factory: recovery app | ota_0: clock | ota_1: clock
@@ -182,6 +183,22 @@ flash (4 MB):  bootloader | nvs | otadata | factory: recovery app | ota_0: clock
 The setup page can also start the clock right away, or keep the recovery app running
 ("Stay in recovery").
 
+**What the display shows**
+
+| Message | Meaning |
+|---------|---------|
+| `Connecting` / `to WiFi...` | The clock firmware is starting |
+| `Getting` / `the time...` | Connected, waiting for the time from the internet (NTP) |
+| `No WiFi` / `12:34` | The clock firmware lost WiFi for more than a minute; the time keeps running |
+| `Crashed!` / `OTA open 15s` | The clock firmware crashed and waits 15 s for an OTA update before it starts again |
+| `Crashed 3x` / `OTA only` | Repeated crashes without the recovery app installed: only OTA for 10 minutes |
+| `Recovery` / reason | The recovery app started (`no WiFi`, `crashed`, `requested`, `power cycled`, `no firmware`) |
+| `WiFi setup:` / `FlipDot-Setup` | Connect to this WiFi to choose another network, see below |
+| `Recovery` / IP address | The recovery app is connected; open this address for the setup page |
+
+The recovery app switches the display off after each message; the dots keep showing it
+without power.
+
 **WiFi setup.** The recovery app keeps trying the stored WiFi. If that fails for 20 s, it
 also opens its own WiFi: **FlipDot-Setup**, with the password `SETUP_AP_PASSWORD` from
 `src/esp32/secrets.h`. Connect a phone to it; the setup page opens by itself (otherwise go
@@ -209,8 +226,9 @@ anyway.
    pio run -e recovery -t erase
    pio run -e recovery -t upload
    ```
-   The recovery app starts (LED double-blinks), connects to the WiFi from `secrets.h`, and
-   waits, because there is no clock firmware yet.
+   The recovery app starts (LED double-blinks, the display shows `Recovery` /
+   `no firmware`), connects to the WiFi from `secrets.h` and shows its IP address. It waits
+   there, because there is no clock firmware yet.
 3. Install the clock firmware **over WiFi**. This also tests that the recovery app works:
    ```sh
    pio run -e esp32 -t upload