Redesign client settings

ClientSettings replaces ConfigEditor: a section list on the left (General,
UI Style, Animations) and the chosen section's settings on the right, each
with a Reset for that section. UI Style shows four theme presets, the
theme colors as a two-column grid, then the radii and font.

New pieces: SectionNav, ThemePresetCard, ColorGrid and Theme.PRESETS.
Theme keeps its config like AnimationConfig does, Divider can be vertical,
and PropertyList's section titles are public.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/main/resources/assets/saturnclient/textures/gui/components/animations.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M22 12h-2.48a2 2 0 0 0-1.93 1.46l-2.35 8.36a.25.25 0 0 1-.48 0L9.24 2.18a.25.25 0 0 0-.48 0l-2.35 8.36A2 2 0 0 1 4.49 12H2"/></svg>

src/main/resources/assets/saturnclient/textures/gui/components/palette.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="13.5" cy="6.5" r="1.5"/><circle cx="17.5" cy="10.5" r="1.5"/><circle cx="8.5" cy="7.5" r="1.5"/><circle cx="6.5" cy="12.5" r="1.5"/><path d="M12 2C6.5 2 2 6.5 2 12s4.5 10 10 10c.926 0 1.648-.746 1.648-1.688 0-.437-.18-.835-.437-1.125-.29-.289-.438-.652-.438-1.125a1.64 1.64 0 0 1 1.668-1.668h1.996c3.051 0 5.555-2.503 5.555-5.554C21.965 6.012 17.461 2 12 2z"/></svg>