feat(input): opt-in WebKitGTK focus repaint workaround for Linux (#342, #782) (#884)

* feat(input): opt-in WebKitGTK focus repaint workaround for Linux (#342, #782)

Some Linux users on WebKitGTK 2.50.x report a freeze when clicking
text fields: the field receives focus (right-click paste still works)
but the canvas never redraws until the window is resized. Likely a
layer-flush / composition scheduling bug in 2.50.x's Skia rendering
pipeline.

Off by default. When enabled in Settings -> System -> Behavior, every
input/textarea focus triggers a sync reflow read plus a one-frame
translateZ(0) toggle on the input's parent so WebKit re-evaluates the
layer tree. Side-effect: search-icon siblings flicker briefly on
focus -- accepted trade-off, only paid by users who opt in.

The toggle row is gated on IS_LINUX and sits next to the existing
Linux WebKitGTK options. The effect subscribes to the auth store and
re-attaches the focusin handler whenever the flag flips, so toggling
off cleanly removes the listener.

* i18n(settings): linux input repaint toggle in all locales

Adds linuxWebkitInputForceRepaint label + description across en, de,
fr, es, nl, nb, ro, zh, ru.

* docs(release): CHANGELOG and credits for linux input freeze workaround (PR #884)

src/locales/es/settings.ts

@@ -204,6 +204,8 @@ export const settings = {
   useCustomTitlebarDesc: 'Reemplaza la barra de título del sistema con una integrada que coincide con el tema de la app. Desactiva para usar la barra nativa de GNOME/GTK.',
   linuxWebkitSmoothScroll: 'Rueda suave (Linux)',
   linuxWebkitSmoothScrollDesc: 'Activado: inercia. Desactivado: pasos por línea (estilo GTK).',
+  linuxWebkitInputForceRepaint: 'Repintar los campos al enfocar (Linux)',
+  linuxWebkitInputForceRepaintDesc: 'Solución para WebKitGTK 2.50.x donde los campos de texto se congelan al pulsar. Las lupas parpadean brevemente al enfocar.',
   linuxWaylandTextRender: 'Renderizado de texto Wayland (Linux)',
   linuxWaylandTextRenderDesc:
     'El suavizado en la interfaz se aplica al instante. La aceleración de hardware de WebKit (nítido/GPU) se guarda y aplica al reiniciar la app; cambiarla en vivo puede congelar WebKitGTK.',