Icons: small images of their own size for pages

Bitmaps that only pages use (backgrounds, images by state) are now icons:
own width and height, stored in /icons, not in the page lists or the Home
Assistant dropdowns. Page backgrounds and image elements use icons or
bitmaps; the renderer gets icons expanded at the top left, so pages look
the same. Web UI: Icons tab with an editor, Make icon / Make bitmap, Save
as icon on the Draw tab, icons in the backup.

A one-time migration in time-boxed steps moves the uploaded bitmaps that
only pages use, after the new firmware is marked good.

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

src/esp32/README.md

@@ -20,6 +20,7 @@ debug output. Wiring is described in the [documentation](../../docs/wiring.md).
 | `logic/settings.*` | The settings of the web UI with their defaults and checks |
 | `logic/schedule.*` | When the display is on (night, clock, standby), from the settings |
 | `logic/bitmap_format.*` | 84 x 19 bitmap format, hex encoding, names of bitmaps, pages and fonts |
+| `logic/icon_format.*` | Icons: small bitmaps of their own size, to and from full screen bitmaps |
 | `logic/page.*` | Dynamic pages: the struct, checks, time slots, texts of the elements (clock, date, Home Assistant value, text) |
 | `logic/page_render.*` | Draws a dynamic page into a bitmap (display and web previews) |
 | `logic/font.*` | Dot font format (built-in and uploaded fonts), text width, drawing |
@@ -40,6 +41,7 @@ debug output. Wiring is described in the [documentation](../../docs/wiring.md).
 | **`display/`** | **What is drawn** |
 | `display/frames.*` | The screens: dynamic page, "No WiFi", page bitmap, live image, off image (`FlipdotFrames`) |
 | `display/bitmap_store.*` | Built-in bitmaps and the uploaded ones on LittleFS |
+| `display/icon_store.*` | Icons (small images for pages) on LittleFS |
 | `display/page_store.*` | Built-in and stored dynamic pages (`/pages/<name>.pg`) |
 | `display/font_store.*` | Built-in and uploaded fonts (`/fonts/<name>.fnt`) |
 | `display/page_resources.*` | Gives the page renderer its bitmaps, fonts and Home Assistant values |