Add optional toast opacity support

[victorycodedev]

What changed?

Added optional opacity support to ToastKit.

Developers can now make a toast translucent by calling opacity():

Toast::success('Saved successfully')
    ->opacity()
    ->show();

Calling opacity() without a value uses 0.8 opacity. A custom value between 0.0 and 1.0 can also be provided:

Toast::success('Saved successfully')
    ->opacity(0.6)
    ->show();

Opacity is completely opt-in. Toasts that do not use opacity() continue to render normally with no change to their existing appearance or behavior.

The feature works across Android and iOS and integrates with existing ToastKit features such as animations, presets, and toast updates.

Why?

This gives developers more control over the appearance of their toasts, making it possible to create softer or translucent toast styles without changing ToastKit's default appearance.

Existing applications are unaffected because opacity is only applied when explicitly requested.

How was it tested?

• Tested the default opacity() value of 0.8.
• Tested custom opacity values.
• Tested minimum and maximum values, including 0.0 and 1.0.
• Tested clamping of values outside the supported range.
• Verified toasts without opacity() retain their existing appearance.
• Verified opacity works with existing animations, presets, and toast updates.
• Ran the existing test suite and plugin validation.

Platforms tested

• PHP
• JavaScript
• Android
• iOS
• Not applicable / documentation only

Breaking changes?

None.

Opacity is opt-in and does not change the appearance or behavior of existing toasts.

Checklist

• Tests were added or updated where appropriate.
• Existing relevant tests pass.
• Documentation was updated where necessary.
• Public API and event/bridge compatibility were considered.
• Android/iOS behavior parity was considered where relevant.
• No unnecessary native dependencies were introduced.
• No secrets, tokens, temporary logging, or debugging code were committed.
• Native changes were tested in a generated NativePHP application where practical.