feat: add customizable build access key UI with paste/restore

[HugeFrog24]

Custom Build Access Key Override

Users will be able to override SKY_BUILD_ACCESS_KEY via Settings UI without needing to rebuild Canvas.

Behavior

Toggle	Input	Result
OFF	—	Uses compiled-in key
ON	Has value	Uses custom key
ON	Empty	Falls back to compiled-in key

Tutorial

• Maintainer: When TGC rotates its Sky build access key, just publish the new key where users can see it (Discord, GitHub, Telegram).
• User: Open Canvas → Settings → Enable toggle → Paste key → Done.
  Instant fix, no rebuild, no waiting for an update.

[MisterGatto]

Will be added in the next release

[HugeFrog24]

Nice, I see it made it into the build @MisterGatto. Good call making it automatic 👌
Happy to mark this resolved.