feat: Media Player Visualizer (cava integration)

[ashlcx]

Feature addition of a cava visualizer to media player. Only shows media is playing through the active player.
Includes configuration options for the following:

Field	Type	Default	Description
show_visualizer	bool	false	Enable or disable the visualizer.
visualizer_bar_count	integer	8	Number of frequency bars to display.
visualizer_framerate	integer	60	Target framerate for CAVA output.
visualizer_padding	integer	3	Horizontal padding around the visualizer canvas (px).
visualizer_color	color	"Text"	Bar colour — see Color below.
visualizer_channels	string	"Stereo"	"Stereo" or "Mono".
visualizer_mono_option	string	"Average"	Mono mix mode: "Average", "Left", or "Right".

Example Config:

[media_player]
show_visualizer = true
visualizer_bar_count = 32
visualizer_color =  { low = "#a6e3a1", mid = "#f9e2af", high = "#f38ba8" }
visualizer_channels = "Mono"
visualizer_mono_option = "Average"

[MalpenZibo]

What if we declare this like optional values? I mean, the user could simply specify gradient and use the base palette (Success -> warn (right now we use a weak danger for this, but after the iced update, there will be a dedicated value) -> danger) and only if necessary override the specific color.