Add Dark mode for a screen beside the bed, with every colour in one table (0.2.63)

Dark mode is a new switch under Brightness on the screen's settings page, in
the Screen settings of ESP Screens and as switch.<screen>_dark_mode in Home
Assistant, so an automation can turn it on at bedtime. The screen changes
look at once, open cards and an alert included, and keeps it after a
restart. The design stays the same: a black page, graphite cards with a
hairline, soft white text, Home Assistant's state colours where they tell
something, and pastel card colours as deeper versions of themselves.

Every colour the firmware chooses now lives in components/smart_display/
theme.h: roles with a light and a dark value, the named card colours and
Home Assistant's state colours. The board profiles give widgets colourless
shared styles that theme.h fills, so a change of look refills those styles
and draws again what code painted by state. The light look is unchanged
apart from merges below one panel step. Dark mode costs 440 bytes of static
RAM on the CYD, and the LVGL tree of the host build is 416 bytes smaller; tests
keep colours out of every other file.

Comparing a screen that switched looks with one that booted in it also
found two older bugs, now fixed: a settings switch that was on showed its
knob at the left whenever its page was drawn, and the sun card's sunlit
area turned orange after a palette change. Firmware 0.2.54.

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

docs/RELEASING.md

@@ -176,6 +176,53 @@ icons sit off-center in the browser); run `generate_packages.py` afterward.
 The `MDI_GLYPH_*` substitutions are retired: `TILEn_ICON` in manual
 profiles must come from the set. No changed preferences or keys.
 
+### Compatibility 0.2.63 / firmware 0.2.54
+
+Firmware (`components/smart_display`, new `theme.h`), both board profiles and the app's settings. The tile protocol
+and the layout message are unchanged; nothing new on the wire.
+
+- **Colours in one table.** `theme.h` holds every colour the firmware chooses: roles with a light and a dark value,
+  the named card colours (`SWATCHES`, moved out of `tile_palette.h`, which now looks them up) and Home Assistant's
+  state colours (`theme::ha`). Headers ask for roles; the profiles give widgets paints (`styles: paint_card`), shared
+  styles without a colour that the profile's `theme::paints` list fills (`theme::fill()`, code in flash rather than a
+  table in RAM). `tests/test_theme.py` fails on a hex colour anywhere else (the light's colour picker and the value
+  card's colour wheel keep their hues) and on a paint that is not defined, filled once and used in every profile and
+  package; `tests/test_theme.cpp` checks the values.
+- **The light look is the old one.** Host renders of every page, card, alert and settings page against firmware
+  0.2.53 are pixel-identical, apart from merges below one panel step: the text of the simple cards (`#202020` to
+  `#1B1B1B`) and of some secondary words (`#5F6368` to `#616161`), the colour card's page (`#F7F7F7` to `#F8F8F8`,
+  what the eye saw through the old sheet), an unavailable tile's circle and the off brightness track (to `#F1F1F1`),
+  a pressed round key (`#DADADA` and `#D9D9D9` to `#DDDDDD`) and the tints of the vacuum's halo and the cover sliders,
+  now computed from their state colour (within two steps of the old hand-picked values), and the two fixes below.
+- **Two redraws that drew differently**, found by comparing a screen that switched looks with one that booted in it,
+  and both older than 0.2.54. `settings_screen::draw()` ends in `refresh()`, whose `move_knob()` read the new track's
+  coordinates before LVGL had laid the page out (still 0 wide), so every switch that was on showed its knob at the
+  left until the next refresh; the knob is now placed from the size `pill()` gave the track (`knob_x()`), and a
+  change of look, which draws the page again, no longer throws the Dark mode switch's own knob to the left. And
+  `render_slot`'s palette gave the sun path's fill the tile's accent (orange) whenever the palette changed, while
+  `render_sunpath` sets the sun's yellow on every render, so the sunlit area changed colour by itself a minute later;
+  the sun path keeps its own fill now.
+- **Dark mode** is `settings_screen::dark_mode` beside the other settings outside the frozen block, with a uint32
+  preference of its own (`0x44524B31`, "DRK1"); `screen_settings::Settings` stays version 1. It is a row under
+  Brightness (five rows: no pager on either board), the template switch `Dark mode` (config, `restore_mode: DISABLED`)
+  and the app's key `dark_mode` (`SETTING_RULES`, `SETTINGS_BESIDE_BLOCK`, `SETTING_ENTITIES`). A screen that gets its
+  settings with the layout never has it: `settings_view` leaves it out, the layout message never carries it.
+  `DARK_MODE_MIN_FIRMWARE` is 0.2.54.
+- **A change of look** runs through `set()` -> `apply_screen_settings` -> `theme::set_dark()`: the profile's and the
+  firmware's own paints are refilled, LVGL is told once (`lv_obj_report_style_change(nullptr)`), and `theme::redraw`
+  (set in `on_boot`) draws again what code painted by state: the tiles' palettes and the top bar
+  (`runtime_tiles::restyle`), an open card in place, the colour card (`light_controls::restyle`), the settings page,
+  an alert that is up (`alert_card_color`) and the climate card and its mode picker. The same pass, so no frame
+  mixes the looks; at boot `set_dark()` runs before the first frame.
+- **Profiles:** the substitutions `BG_TOP_COLOR`, `BG_BOTTOM_COLOR` and `ACCENT_*` are gone (an override that set them
+  has no effect any more), `style_bg_grad` is `style_page` (one fill, no gradient between two equal stops), the four
+  unused `*_disabled` styles and the colour card's `color_detail_bg` and `color_detail_scrim` are removed, and
+  `open_value_overlay` lost its three colour parameters (the value card's slider takes paints).
+- App 0.2.63 with firmware 0.2.53 or older: no Dark mode row, everything else as before. Firmware 0.2.54 with an
+  older app: Dark mode works on the screen and in Home Assistant; the older editor does not show the row.
+- A layout of a screen that gets its settings with the layout is stored with `dark_mode` among its settings. An app
+  from before 0.2.63 refuses that key: restore the data backup when rolling back, as for every settings key before.
+
 ### Compatibility 0.2.62 / firmware 0.2.53
 
 Firmware (`components/smart_display`), the icon fonts and the top bar's icon. Storage, tile protocol, preferences and