Extend waveform module with additional styles

[aurexav]

Context: Floating panel notes list deferred waveform styles (mirrored bars, dots, continuous line).

Scope:

• Add at least one additional waveform style.
• Provide a way to select styles (initially internal or via settings).

Reference: docs/guide/development/ui_floating_panel_notes.md (Deferred enhancements).

Acceptance:

• New waveform style(s) implemented.
• Style selection documented.