Add Civ Lite audio controls and cues

[YfengJ]

Summary

• Add a lazy Web Audio manager for Civ Lite with persisted master/music/SFX settings.
• Add sidebar controls for mute, theme selection, and volume sliders.
• Map gameplay actions to procedural SFX for click, selection, movement, attacks, building, end turn, victory, and defeat.

Validation

• node --test demo/civ-lite/audio-model.test.mjs
• node --check demo/civ-lite/audio-model.js
• node --check demo/civ-lite/game.js
• node --check demo/civ-lite/sprites.js
• git diff --check
• Playwright smoke on http://127.0.0.1:4196/demo/civ-lite/: audio controls rendered, mute/theme/volume controls responded, localStorage persisted volume, canvas pixel sample was non-empty.

Closes #25

[YfengJ]

CI note: the failing Build Godot Web export job is stopping at the existing Godot export preset configuration error: Cannot export project with preset Web due to configuration errors. This PR only changes demo/civ-lite JS/HTML/CSS and adds a local Node test for the audio model. Local validation passed: node --test demo/civ-lite/audio-model.test.mjs; node --check demo/civ-lite/audio-model.js; node --check demo/civ-lite/game.js; node --check demo/civ-lite/sprites.js; git diff --check; and a Playwright smoke test for the Civ Lite page, audio controls, localStorage persistence, and non-empty canvas rendering.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud