feat: add Compound Design System token overrides

[YourSandwich]

Summary

• Adds a compound key to theme JSON with overrides for Element's Compound Design System (CPD) tokens
• Element has migrated many UI components from legacy CSS variables to CPD tokens, causing themes to not apply to sidebars, panels, dialogs, emoji pickers, context menus, and other newer UI elements
• All 56 themes (4 flavors x 14 accents) regenerated with the new compound section

Token coverage

• Gray scale: 14 steps mapped to the full Catppuccin palette progression (crust → mantle → base → surface → overlay → subtext → text)
• Color scales (red, orange, yellow, green, blue, purple, cyan, pink, lime, fuchsia): 14-step scales generated via mix filter, blending each palette color with crust (dark end) and text (light end)
• Semantic tokens: text, background, icon, and border tokens mapped to appropriate palette colors with per-accent awareness
• Dark and light theme variants handled separately with inverted scale directions

Tested with

• Element Desktop Nightly (latest) on Linux
• Catppuccin Macchiato (Lavender) flavor
• Verified: sidebars, room list, timeline, dialogs, emoji picker, context menus, right panel, pinned messages, Element Call widget

Fixes #19

Test plan

• Select any Catppuccin theme in Element Desktop/Web
• Verify sidebar, room list panel, and space panel use Catppuccin palette colors
• Verify dialogs, emoji picker, and context menus are themed
• Verify right panel (room info, user info) is themed
• Test with both dark (Macchiato/Mocha/Frappe) and light (Latte) flavors
• Verify accent color appears in accent-colored UI elements

🤖 Generated with Claude Code

[YourSandwich]

Unfortunately I did not found a method to skin element-call accordingly beside patching the webapp.asar directly

[bartkor12]

Tested on develop.element.io with the Macchiato (Lavender) theme by copy-pasting its json link into the custom theme section. The sidebar is not correctly themed.

[spookyintheam]

Thanks for the PR @YourSandwich!

I am pretty low in bandwidth for Catppuccin, so In case you're open to taking over this port, we can discuss on the Catppuccin discord server.

[YourSandwich]

Hi @spookyintheam thank you for the offer, I am only available here and on matrix (@sandwich:archworks.co)
I wouldn't mind taking this over if I find a better way to generate the CSS.

But for CSS specifically I do not feel confident that I could provide code in the best practice manner.