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/isometric.md

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+# Isometric
+
+## Overview
+3D-like objects rendered in isometric projection — no perspective, parallel lines.
+
+## Rendering Characteristics
+
+| Property | Value |
+|----------|-------|
+| **Detail level** | Medium to high — clean geometry |
+| **Lighting** | Flat or subtle ambient |
+| **Texture** | Smooth, clean surfaces |
+| **Color** | Brand palette, can be vibrant |
+| **Depth** | Isometric projection (30-degree angles) |
+
+## Prompt Keywords
+`isometric, isometric illustration, 3D isometric, parallel projection, geometric, clean, technical illustration`
+
+## Best For
+- Tech products, data visualization, process diagrams, feature showcases
+- Explaining complex systems or workflows visually
+
+## Dimensions Guide
+- Scene: 16:9 or square
+- Individual objects: 1:1 ratio
+- Infographics: variable height