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>

src/esp32/README.md

@@ -25,7 +25,9 @@ debug output. Wiring is described in the [main README](../../README.md#wiring-be
 | `system/boot_target.*` | Switching between the clock firmware and the recovery app |
 | `system/system_store.*` | Settings in NVS: WiFi, recovery reason, firmware slot and version, power-on count |
 | **`display/`** | **What is drawn** |
-| `display/frames.*` | The screens: clock, logo, blank, text (`FlipdotFrames`) |
+| `display/frames.*` | The screens of the clock: clock, "No WiFi", logo, blank (`FlipdotFrames`) |
+| `display/status_screen.*` | Two-line status messages at boot, after a crash and in the recovery app (`StatusScreen`) |
+| `display/text.*` | Centered text lines on the 84 x 19 display |
 | `display/bitmaps.h` | 1-bit bitmaps (Pikachu, thought bubble, Nintendo logo, ...) |
 | **`nano_link/`** | **Connection to the Nano** |
 | `nano_link/nano_link.*` | Relay and serial link: power on (waits for `READY`), power off, bootloader start (`NanoLink`) |
@@ -74,6 +76,11 @@ Rules for changing the code:
 
 ## Features
 
+- **Status on the display:** `Connecting to WiFi...` and `Getting the time...` at boot,
+  `Crashed!` messages in the OTA-only modes, and `No WiFi` with the time when WiFi is down
+  for more than a minute. See the table in the
+  [main README](../../README.md#recovery-app).
+
 - **Frames only when something changes:** a new frame is sent when the minute changes, the
   screen changes (clock, logo, blank) or the Nano was just powered on. The serial line is
   quiet in between, which also gives the Nano time for its periodic full redraw.