Show a live picture on a camera tile, run an action from the alert button, roll long media titles, and keep full-page tiles in their own colour (0.2.91)

Live picture (issue #4): a camera or image tile on a Guition takes
Display -> Live picture with a pace of 15 or 30 s. The camera tiles of a
page share one download: the screen asks ESP Screens for them together
(esphome.screen_camera with tiles, size and bg) and the app serves one
BMP, a strip of squares with the corners rounded over each tile's own
colour; every tile draws its square out of it with LVGL's image offset
(LV_IMAGE_ALIGN_TOP_LEFT: the default centres a taller source). A third
online_image on the Guition holds the strip; it loads after the alert's
picture, a cover and the camera full screen, never under a card, in
standby or under a finger. The strip is served whole every time: ESPHome's
http_request logs a 304 as a failed request. Firmware 0.2.77.

Alert button: esp_screens_show_alert takes action and data; the app
performs the action once when the button's report (esphome.screen_alert,
ok) comes from any screen. show_alert keeps its seven fields, so every
firmware from 0.2.31 has it.

Media card and full-page media tile: a title or artist line that is too
wide rolls by (LV_LABEL_LONG_SCROLL_CIRCULAR) instead of ending in dots.

Full-page tiles are white or their own pastel like every other tile; the
tint in the state colour of firmware 0.2.62 to 0.2.76 is gone.

Host harness (27 checks) and bench Guition + local add-on on the Yellow:
docs/TEST_RESULTS_0291.md. CYD firmware 1,633,728 B, 89.0 %.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_runtime_model.cpp

@@ -188,8 +188,8 @@ static void test_slider_colours() {
   setpoint.state = "55.0"; assert(setpoint.slider_active());
 }
 struct RunSliderColours { RunSliderColours() { test_slider_colours(); } } run_slider_colours;
-// Home Assistant's stateActive() (firmware 0.2.71+): what it calls inactive is grey on the screen, and only a tile
-// that can be off lights up over a whole page, while it is on.
+// Home Assistant's stateActive() (firmware 0.2.71+): what it calls inactive is grey on the screen. (`lights` was the
+// full-page tint of firmware 0.2.62 to 0.2.76, gone since 0.2.77: the cases stay as a record of the rule.)
 static void test_state_active() {
   using namespace runtime_tiles;
   struct Case { const char *entity, *state; bool active, lights; };
@@ -219,12 +219,12 @@ static void test_state_active() {
            {"scene.a", "unavailable", false, false}}) {
     Tile t; t.entity = c.entity; t.state = c.state; t.received = true;
     assert(t.active() == c.active);
-    assert(t.lights_up() == c.lights);
+    (void) c.lights;
   }
-  // Nothing received yet is inactive; a built-in card has no state, is always active and never lit.
-  { Tile t; t.entity = "light.a"; t.state = "on"; assert(!t.active() && !t.lights_up()); }
+  // Nothing received yet is inactive; a built-in card has no state and is always active.
+  { Tile t; t.entity = "light.a"; t.state = "on"; assert(!t.active()); }
   for (const char *entity : {"screen.clock", "screen.settings", "screen.page_2"}) {
-    Tile t; t.entity = entity; assert(t.active() && !t.lights_up());
+    Tile t; t.entity = entity; assert(t.active());
   }
   // A closed blind: grey card, coloured slider.
   { Tile t; t.entity = "cover.a"; t.state = "closed"; t.received = true; assert(!t.active() && t.slider_active()); }