[Icons] Migrate UI glyphs to palette-token SVGs (#7595)

* [Icons] Migrate UI glyphs to palette-token SVGs

Runtime inversion is not a theming system: it rotates hue, breaks duotone art
and mishandles alpha, and a QPixmap snapshot cannot follow a palette change.
Redraw the top-level UI glyph set on a 24x24 grid with `currentColor` as the
paint token, drop Inkscape/Sodipodi cruft, and delete the icons whose metaphor
was duplicated (cogwheel/gear -> settings, scale_balanced -> scales,
update.png -> reload).

Load the glyphs through `loadThemedIcon` so the engine resolves the token from
the palette on every request, and let `themePixmap` use the same resolution for
one-shot pixmaps. `loadColorAdjustedPixmap` is gone; every caller now keeps a
QIcon, which `SettingsButtonWidget::setButtonIcon` accepts instead of a QPixmap.

Content art (mana, counters, countries) keeps its authored colors.

Add a render test covering aspect ratio, palette flips, icon modes and
high-DPI pixmaps.

* [Tests] Keep the icon render test QApplication alive until exit

Creating it as a function-local static tears it down before Qt's library statics
at exit, and libQt6Network then runs QObject destructors against freed memory —
a SEGV the sanitizer leg reports after the tests have already passed. Leak the
application instead, the usual pattern for a test binary.

* [Icons] Render lock and dropdown glyphs through the icon engine

Both generators rendered the sentinel SVG to a fixed height x height pixmap
at DPR 1. The pre-migration path rendered larger and let QIcon scale it, so
on a 2x display the games-list lock (13px) and the banner dropdown arrow
(24px) came back crisp; the new path hands the widget a DPR-1 bitmap that
gets upscaled and blurred.

- The games list asks the themed engine for `icons/lock` directly, so the
  item view paints it at the device pixel ratio and the lock also follows
  HighlightedText on a selected row.
- The dropdown goes through `loadThemedIcon(...).pixmap(size, dpr)`, which
  keeps the glyph's aspect ratio and renders at the requested ratio.
- LockPixmapGenerator has no consumer left, so it and its cache are gone.

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

tests/theme_migration/CMakeLists.txt

@@ -5,12 +5,14 @@ cockatrice_add_test(
   ${CMAKE_SOURCE_DIR}/cockatrice/src/interface/theme_manager.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/interface/theme_config.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/interface/pixel_map_generator.cpp
+  ${CMAKE_SOURCE_DIR}/cockatrice/src/interface/theme_icon.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/client/settings/cache_settings.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/client/settings/card_counter_settings.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/client/settings/shortcuts_settings.cpp
   ${CMAKE_SOURCE_DIR}/cockatrice/src/client/network/update/client/release_channel.cpp
   ${VERSION_STRING_CPP}
   theme_migration_test.cpp
+  theme_icon_render_test.cpp
   LIBS
   libcockatrice_settings
   libcockatrice_network
@@ -18,4 +20,6 @@ cockatrice_add_test(
   libcockatrice_protocol
   INCLUDE_DIRS
   ${CMAKE_SOURCE_DIR}/cockatrice/src
+  DEFINITIONS
+  COCKATRICE_SOURCE_DIR="${CMAKE_SOURCE_DIR}"
 )