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

.claude/skills/wds-4-ux-design/data/modular-architecture/02-workflows/02-file-structure.md

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+# Storyboard File Structure
+
+**Where to store storyboards in the three-tier architecture**
+
+---
+
+## Storage Location
+
+```
+project-root/
+├─ Pages/
+│  └─ 02-calendar-page.md
+│
+├─ Components/
+│  └─ walk-slot-card.component.md
+│
+├─ Features/
+│  ├─ walk-booking-logic.feature.md
+│  └─ Storyboards/                    ← Store here
+│     ├─ walk-state-transitions.jpg
+│     ├─ booking-flow.jpg
+│     └─ calendar-sync-flow.jpg
+│
+└─ Sketches/                          ← Page sketches
+   └─ 02-calendar-page-sketch.jpg
+```
+
+---
+
+## Why Features/Storyboards/?
+
+Storyboards document **functionality**, not visual design:
+
+- State transitions (functional)
+- User interactions (functional)
+- Business logic flows (functional)
+
+Therefore, they belong with **Features**, not Components.
+
+---
+
+## Reference Pattern
+
+**From Feature File:**
+
+```markdown
+Features/walk-booking-logic.feature.md
+
+## Visual Storyboard
+
+![Walk State Transitions](Storyboards/walk-state-transitions.jpg)
+```
+
+**From Component File:**
+
+```markdown
+Components/walk-slot-card.component.md
+
+## Visual States
+
+See storyboard for state transitions:
+→ Features/Storyboards/walk-state-transitions.jpg
+```
+
+---
+
+## Separation from Page Sketches
+
+**Page Sketches** (Sketches/ folder):
+
+- Show page layout
+- Static view of entire page
+- Used during initial design
+
+**Storyboards** (Features/Storyboards/ folder):
+
+- Show component behavior
+- Sequential frames showing changes
+- Used during specification
+
+---
+
+## Next Steps
+
+- [Naming Conventions](02-naming-conventions.md)
+- [Feature File Integration](feature-file-integration.md)