Show a spinner while a screen starts and while a camera loads, bring a camera's first picture sooner, and round the alert's camera picture (0.2.87)

Starting screen: until the first layout, render() keeps the status text
("Connecting to Home Assistant", "Waiting for ESP Screens") and a spinner
as one block in the middle of the page; the first layout deletes both.
The room label stays empty meanwhile, and ROOM_NAME defaults to "".

Camera: the full screen shows a spinner instead of "Loading image". The
screen asks when the camera opens and loads a link as soon as it comes
(camera_load, never under a finger) instead of waiting for the 250 ms
tick twice, and online_image reads 16 KB per loop instead of 4 KB. On the
bench Guition with the EZVIZ camera: cold 5.8 -> 4.55 s, warm 3.4 -> 2.06 s.

Alert picture: the image takes the frame's radius (18, the alert card's);
LVGL's software renderer clips it row by row, without a layer.

One spinner_create() makes the busy sheet's, the starting screen's and the
camera's spinner; theme role CAMERA_TRACK colours the camera's ring. The
README gets a row of camera pictures; docs/CAMERA.md, RELEASING.md and
TEST_RESULTS_0287.md describe the measurements.

Checked with tools/check.sh (473 Python tests, 19/19 C++, editor) and
--firmware: CYD 1,678,816 B (91.5 %, +1,312 B), Guition 2,055,280 B
(25.3 %). Host renders of both boards in both looks; four OTA builds on
the bench Guition Wallbox, which runs this firmware.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -17,7 +17,7 @@ lights, the heating or the vacuum.
 
 **What.** Firmware for two affordable panels, the 2.8-inch CYD and the 4-inch Guition, with up to
 48 tiles over eight pages: lights, climate, blinds and curtains, the vacuum, media, the weather,
-history graphs, clocks and timers. A tile can take the whole page, one big switch you push without
+history graphs, clocks and timers, and on a Guition your cameras. A tile can take the whole page, one big switch you push without
 looking, and a tile can go to another page. An automation can put an alert on every screen when someone rings
 the bell, and a Guition shows who is there with the doorbell camera's picture. A tap can run any
 action Home Assistant has for a tile, and Dark mode suits a screen beside the bed.
@@ -62,6 +62,12 @@ also be changed on the screen or by an automation, and your own YAML for one scr
   <img src="docs/images/guition-dark-media.png" width="32%" alt="The media card in dark mode: the same cover and keys on a black page">
 </p>
 <p align="center"><sub>Tap a tile to switch it, hold it for the full card. Keys and sliders right on the tile, pastel colors, a clock, the weather and history you can read with a finger. A lamp with modes (a WLED) gets an effects page with a drum picker, named and filled from what Home Assistant lists for it. The media card shows what plays with its album cover, fetched by ESP Screens like a camera picture (<a href="docs/CAMERA.md">how</a>). Rendered from the firmware's own LVGL code with a demo home.</sub></p>
+<p align="center">
+  <img src="docs/images/guition-camera-tiles.png" width="32%" alt="Cameras as tiles on the Guition: the front door camera, the garden camera live, the doorbell's last ring, next to the door, the porch light and the garage door">
+  <img src="docs/images/guition-camera.png" width="32%" alt="A camera tile tapped: the front door camera full screen, with the round back key and the camera's name at the top">
+  <img src="docs/images/guition-alert-camera.png" width="32%" alt="The same camera in an alert: its picture across the top of the card, with the card's rounded corners">
+</p>
+<p align="center"><sub>Cameras are tiles too, not only part of an alert: any camera or snapshot in Home Assistant (a doorbell's last ring, for example) goes on a Guition like any other tile. Tap it for the picture full screen, refreshed every four seconds; an alert can carry the same picture. The CYD has no memory for pictures (<a href="docs/CAMERA.md">how it works</a>).</sub></p>
 <p align="center">
   <img src="docs/images/cyd-home.png" width="32%" alt="CYD 2.8-inch screen: the weather forecast, a kitchen timer, the coffee machine, a lamp and power usage as a large value">
   <img src="docs/images/cyd-page-2.png" width="32%" alt="Second CYD page: Sonos volume, presence, a scene and an energy graph">