feat(icons): split built-in sprite into per-icon SVG sources and add ticket icon

Move the 114 built-in sprite icons out of assets/js/runtime/svg-icon.js into
assets/icons/sprite/{key}.svg and generate svg-icon.js with
tools/build-svg-sprite.mjs. Add ticket-color and use it for the user center
ticket entry. Update sidebar contract tests for the creator card labels.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/icons/sprite/signout.svg

@@ -0,0 +1 @@
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