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

.agents/skills/wds-6-asset-generation/data/styles/content-styles/pencil-sketch.md

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+# Pencil Sketch
+
+## Overview
+Hand-drawn pencil or charcoal look — raw, authentic, in-progress feel.
+
+## Rendering Characteristics
+
+| Property | Value |
+|----------|-------|
+| **Detail level** | Variable — from rough to refined |
+| **Lighting** | Tonal shading, crosshatch |
+| **Texture** | Paper grain, graphite smudge |
+| **Color** | Grayscale (or limited color accents) |
+| **Depth** | Tonal depth through shading |
+
+## Prompt Keywords
+`pencil sketch, hand-drawn, graphite, charcoal, sketch style, rough drawing, crosshatch, tonal`
+
+## Best For
+- Architecture, concept art, wireframe-style illustrations, draft previews
+- Conveying "in progress" or "behind the scenes" feel
+
+## Dimensions Guide
+- Concept sketches: variable
+- Wireframe illustrations: page-width