feat: design system overhaul — sidebar, AI chats, settings, brainstorm, color cleanup

- Sidebar: dynamic brand-accent colors, brainstorm section restyled
- AI chat general: popup panel with expand/collapse, hides when contextual AI open
- AI chat contextual: tabs reordered (Actions first), X close button, height fix
- Settings: all tabs restyled, 6 new color presets (sage, terracotta, iron, etc.)
- Global color cleanup: emerald/orange hardcoded → brand-accent dynamic
- Brainstorm page: orange → brand-accent throughout
- PageEntry animation component added to key pages
- Floating AI button: bg-brand-accent instead of hardcoded black
- i18n: all 15 locales updated with new AI/billing keys
- Billing: freemium quota tracking, BYOK, stripe subscription scaffolding
- Admin: integrated into new design
- AGENTS.md + CLAUDE.md project rules added

.agent/skills/wds-6-asset-generation/data/styles/design-styles/brutalist.md

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+# Brutalist
+
+## Overview
+Raw, bold, unapologetic design that breaks conventions intentionally.
+
+## Visual Characteristics
+
+| Property | Value |
+|----------|-------|
+| **Whitespace** | Irregular — sometimes dense, sometimes empty |
+| **Color palette** | High contrast — black/white, neon accents |
+| **Typography** | Bold, oversized, mixed weights, sometimes monospace |
+| **Borders** | Thick, visible, sometimes raw |
+| **Shadows** | Hard/offset shadows or none |
+| **Imagery** | Raw, unprocessed, collage-style |
+| **Icons** | Custom, hand-drawn, or deliberately crude |
+
+## Prompt Keywords
+`brutalist, raw, bold, unconventional, stark, industrial, exposed structure, anti-design`
+
+## Best For
+- Creative agencies, art portfolios, experimental projects, fashion
+- Brands that want to stand out through contrast
+
+## Avoid
+- Healthcare, finance, government, accessibility-critical applications