Add official PlanetScale plugin brand assets

[SimeonGriggs]

Summary

• Recreates feat: add plugin brand assets #4 on a maintainer branch so main receives a GitHub-verified signature.
• Adds official PlanetScale logo marks for composer and catalog surfaces, including a white dark-mode variant.
• Includes brand assets in release archives.

Test plan

• Confirm interface.composerIcon, interface.logo, and interface.logoDark paths resolve
• Confirm both SVGs render as the PlanetScale mark
• Confirm the release archive step includes assets/

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