Add Recording Controls to GUI

[OpenSauce]

Recording is still disabled whilst I figure out the best way to communicate between threads

[Copilot]

Pull Request Overview

Adds GUI controls and backend hooks to manage audio recording state without enabling recording by default.

• ProcessorManager now accepts an optional Recorder and provides a stubbed enable_recording method.
• New StartRecording/StopRecording messages and UI buttons with status indicator in the Control widget.
• AmplifierApp state and message handling updated to wire recording commands to the processor manager.

Reviewed Changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/io/manager.rs	Updated ProcessorManager::new signature and stubbed out enable_recording
src/gui/messages.rs	Added StartRecording and StopRecording message variants
src/gui/components/widgets/common.rs	Removed local ICONS_FONT and imported from the shared constant
src/gui/components/mod.rs	Introduced global ICONS_FONT constant
src/gui/components/control.rs	Added record/stop buttons and status text to the Control layout
src/gui/app.rs	Added is_recording state, message handlers for recording, and passed flag to Control

Comments suppressed due to low confidence (2)

src/io/manager.rs:60

• Consider adding unit tests for enable_recording (and the eventual disable_recording) to verify that the recorder state transitions are handled correctly.

    pub fn enable_recording(&mut self) -> Result<()> {

src/io/manager.rs:66

• There is no disable_recording method in ProcessorManager, yet the GUI calls it. Implement disable_recording(&mut self) to properly stop and drop the recorder.

    }