fix(linux): use gtk_window_set_geometry_hints instead of gdk_window_set_geometry_hints to enforce size limits

[axel10]

Description

This pull request fixes sizing constraint issues on Linux/GTK.

Previously, constraints such as:

• setMinimumSize
• setMaximumSize
• setAspectRatio

were not taking effect correctly.

Problem

Currently, the Linux plugin implementation uses the low-level GDK function:

gdk_window_set_geometry_hints(
    get_gdk_window(self),
    &self->window_geometry,
    self->window_hints
);

This approach has two major flaws:

1. Silent Failure during Window Initialization

If size limits are configured before the window is realized (which is the standard practice during application setup),:

get_gdk_window(self)

(which calls gtk_widget_get_window) returns nullptr.

As a result, geometry hints are silently discarded and never applied.

2. GTK Layout Override

Since GTK maintains its own layout and window state abstraction, raw constraints sent to the underlying GdkWindow are often:

• Overridden by GTK's layout loop.
• Bypassed during resize operations.
• Inconsistent with GTK's internal window state.

Solution

Replace gdk_window_set_geometry_hints with the high-level GTK API gtk_window_set_geometry_hints, targeting the GtkWindow directly:

gtk_window_set_geometry_hints(
    get_window(self),
    nullptr,
    &self->window_geometry,
    self->window_hints
);

When targeting the GtkWindow directly:

• GTK registers and caches the constraints internally.
• Constraints are automatically applied when the window is realized.
• Size restrictions are properly enforced during GTK's resize/layout lifecycle.

This ensures that window sizing constraints work correctly and consistently on Linux/GTK.