feat(theme): add black_panther and killmonger themes (@Pothish69)

[Pothish69]

---- black_panther ----

Description

Adds a new "Black Panther" theme inspired by the Wakandan royal / vibranium
purple palette. It uses a deep purple background with white text for highcontrast.

--- Checks ---

• Add theme to packages/schemas/src/themes.ts
• Add theme to frontend/src/ts/constants/themes.ts
• (optional) Add theme css file to frontend/static/themes
• screenshots of the theme, with different test settings (colorful, flip colors)

--- screenshots for black panther ---

---- killmonger ----

Description

Adds a new "Killmonger" theme inspired by the character's gold-and-black color
scheme. It uses a near-black background with gold accents and white text.

Checks

• Add theme to packages/schemas/src/themes.ts
• Add theme to frontend/src/ts/constants/themes.ts
• (optional) Add theme css file to frontend/static/themes
• screenshots of the theme, with different test settings (colorful, flip colors)

--- screenshot for killmonger---

[Pothish69]

suggest any changes!