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/content-styles/line-art.md

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+# Line Art
+
+## Overview
+Pure outlines — no fill, no shading, just clean continuous lines.
+
+## Rendering Characteristics
+
+| Property | Value |
+|----------|-------|
+| **Detail level** | Low to medium — defined by lines only |
+| **Lighting** | None — no shading |
+| **Texture** | None — clean strokes |
+| **Color** | Single color (usually black) or thin color lines |
+| **Depth** | Implied through line weight variation |
+
+## Prompt Keywords
+`line art, line drawing, outline, continuous line, single line, clean lines, black and white, monoline`
+
+## Best For
+- Icons, technical diagrams, coloring-book style, decorative patterns
+- Minimalist brands, loading animations base art
+
+## Dimensions Guide
+- Icons: 24x24 to 128x128
+- Decorative: variable
+- Diagrams: content-dependent