Add global app color-scheme API with repaint support

[crispy-computing-machine]

Summary

• Added a new public API wb_set_color_scheme(array $options) to configure app-wide visual styling.
• Implemented a native global scheme model (WBCOLORSCHEME) in WinBinder core.
• Applied global colors during control color messages (WM_CTLCOLOR*) so text/background updates propagate across controls.
• Added WM_ERASEBKGND handling to repaint backgrounds with either a solid color or configurable bitmap image and optional client-border tint for top-level windows.
• Added full-window redraw propagation after scheme updates so existing controls repaint immediately.
• Updated stubs and exports so the new API is discoverable from PHP.

New API

wb_set_color_scheme(array $options): bool

Supported keys:

• enabled (bool)
• background_color (int RGB)
• text_color (int RGB)
• border_color (int RGB)
• background_image (string path to BMP)

Notes

• Background images are loaded via LoadImage(..., IMAGE_BITMAP, LR_LOADFROMFILE).
• Theme updates are global and trigger redraw of registered WinBinder windows/children.

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Codex Task