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-4-ux-design/data/modular-architecture/02-workflows/01-what-are-storyboards.md

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+# What Are Storyboards?
+
+**Visual documentation of component functionality**
+
+---
+
+## Definition
+
+A **storyboard** is a visual sequence showing:
+
+- State transitions (empty → loading → active → completed)
+- User interactions (click, type, swipe)
+- System responses (updates, animations, feedback)
+- Time-based changes (countdowns, timers)
+
+---
+
+## Format
+
+**Hand-drawn sketches** (recommended):
+
+- Quick to create
+- Easy to iterate
+- Focus on functionality, not polish
+
+**Example:** TaskFlow `task-status-states.jpg`
+
+- 6 frames showing walk states
+- Numbered sequentially
+- Annotated with triggers
+
+---
+
+## Purpose
+
+Storyboards answer:
+
+- "What does this look like in each state?"
+- "How do users move between states?"
+- "What triggers each transition?"
+- "What happens over time?"
+
+---
+
+## Why Visual?
+
+**Text description:**
+
+```
+When the user books a walk, the card changes to gray,
+the leaderboard updates, and the week overview changes.
+```
+
+**Storyboard:**
+
+```
+Frame 1: WHITE card with "Book" button
+Frame 2: User taps "Book"
+Frame 3: GRAY card, leaderboard +1, week circle gray
+```
+
+Visual is **faster to understand** and **harder to misinterpret**.
+
+---
+
+## Next Steps
+
+- [When to Use Storyboards](01-when-to-use.md)
+- [Storyboard Types](01-storyboard-types.md)
+- [Creation Guide](creation-guide.md)