Finish threading the accent colour through the whole desktop

The recent accent-colour setting only reached part of the desktop.
looks.lua still hardcoded the focused-window border and glow to blue,
so any hyprctl reload -- or every fresh session, for about a second --
reverted a chosen accent; it now reads accentName the same way it
already read colorScheme. The lock screen and terminal stayed blue
regardless of the chosen accent despite the setting's own description
claiming otherwise; panama-lock and panama-theme-apps now resolve and
apply the real accent.

AccentPicker built its swatch model from Theme.accents directly
instead of the schema's own options list, so the two could drift
silently; switched it to read the schema. Its hit target only covered
the swatch, not the name label added specifically for colour-vision
accessibility -- extended to the whole row. Settings search had no
route for the "appearance" group, so searching for the accent or
colour scheme landed on Home.

ColorScheme's hex-to-Hyprland helper assumed 6-digit colours and would
silently corrupt a future translucent one; fixed it to read from the
end of the string instead of the start. An accent-only change no
longer reruns the full colour-scheme pipeline. The gradient it builds
for the focused border now goes through SystemSettings' existing
serialiser instead of a second, under-escaped copy of the same logic.

The settings-ownership contract test enforced the old rule that
ColorScheme must never touch the focused border; updated it to verify
the real, intended rule instead of contradicting the code.

Claude-Session: https://claude.ai/code/session_01E6TJUAh41HaP25MVHWkhRZ

config/dot/quickshell/services/SettingsSearch.qml

@@ -26,6 +26,7 @@ Singleton {
     // entry here still appears in results and routes to Home rather than being
     // dropped, so adding a group can never make a setting unreachable.
     readonly property var groupPages: ({
+        "appearance": "appearance",
         "clock": "appearance",
         "vitals": "appearance",
         "typography": "appearance",