EWW: Hotkey indicators and performance improvements

[kajusnau]

Description of changes

1. Added Hotkey Indicators:

   • Hotkey indicators are simple, non-interactive widgets designed to display changes in volume and brightness.
   • The indicators appear only on the built-in display (display:0) when volume or brightness events are detected.
   • Note that the hotkey indicators will not appear when the Quick Settings widget is open. This is by design.

2. Volume Mute Button In Quick Settings:

   • Volume can now be muted by clicking the speaker icon in the Quick Settings widget.

3. Volume Icon Now Accurately Displays Muted State

4. Changed From Polling To Event Listeners:

   • Replaced some polling variables with event listeners to enhance efficiency.
   • Added the get_mut option in audio-ctrl script to retrieve the current mute status.
   • Adjusted audio-ctrl script to automatically unmute audio if a volume level change is detected. This change affects Ghaf as a whole, due to most (if not all) audio control being done through audio-ctrl.

5. UI & Formatting Clean-up:

   • Cleaned up .yuck and .scss formatting for better readability and maintainability.
   • Removed unused widgets and styles.
   • Moved color definitions to .scss for easier theming and maintenance.

Known Issues/Limitations:

1. Bluetooth Status Not Currently Fetched

   • More investigation needed to find a good way of listening for bluetooth events and updating status.

2. Hotkey Indicator May Become Slow To Respond

   • Hotkey indicator may slow down and appear to "lag" when multiple brightness and volume events are triggered at the same time.

Checklist for things done

• [x] Summary of the proposed changes in the PR description
• [x] More detailed description in the commit message(s)
• [x] Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• [x] Contribution guidelines followed
• [ ] Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• [ ] PR linked to architecture documentation and requirement(s) (ticket id)
• [x] Test procedure described (or includes tests). Select one or more:
  • [x] Tested on Lenovo X1 x86_64
  • [ ] Tested on Jetson Orin NX or AGX aarch64
  • [ ] Tested on Polarfire riscv64
• [ ] Author has run make-checks and it passes
• [x] All automatic Github Action checks pass - see actions
• [x] Author has added reviewers and removed PR draft status
• [ ] Change requires full re-installation
• [x] Change can be updated with nixos-rebuild ... switch

Instructions for Testing

• [x] List all targets that this applies to: Lenovo X1
• [x] Is this a new feature
  • [x] List the test steps to verify: Can be tested on Lenovo X1 following usual installation or nixos-rebuild ... switch
• [x] If it is an improvement how does it impact existing functionality? Listed in the description above.

[milva-unikie]

Tested on Lenovo-X1 (nixos-rebuid switch)

• Works well
• Looks good
• Test-automation passes