Add selectable Muledump color scheme

[TadusPro]

Summary

Adds an optional Muledump-inspired color scheme using the palette from TadusPro/muledump.

• Adds three direct theme choices: Dark, Light, and Muledump.
• Keeps EAM’s existing dark and light themes unchanged.
• Persists the selected color scheme in the existing user settings.
• Applies Muledump colors to backgrounds, cards, text, controls, selected sidebar items, gradients, and notifications.
• Adds Muledump-styled Vault Peeker empty slots.
• Fixes transparent empty slots in the newer Vault Peeker canvas renderer.
• Keeps gameplay-specific colors, such as item rarity colors, unchanged.

Testing

• Production Vite build completes successfully.
• Visually tested all three theme choices.
• Verified Muledump styling across the main UI and Vault Peeker.
• Verified empty inventory, equipment, and backpack slots remain visible.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics -107 complexity · 2 duplication

Metric	Results
Complexity	-107
Duplication	2

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