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-0-project-setup/templates/folder-guides/00-product-brief.template.md

@@ -0,0 +1,59 @@
+# Product Brief: {{project_name}}
+
+> The strategic foundation — why this product exists, who it serves, and what success looks like.
+
+**Created:** {{date}}
+**Phase:** 1 — Product Brief
+**Agent:** Saga (Analyst)
+
+---
+
+## What Belongs Here
+
+The Product Brief answers five strategic questions:
+
+1. **Why** does this product exist? (Vision & business goals)
+2. **Who** is it for? (Target users and their context)
+3. **What** does it need to do? (Core capabilities)
+4. **How** will we know it works? (Success metrics)
+5. **What** are the constraints? (Platform requirements, tech stack)
+
+Everything downstream — trigger maps, scenarios, page specs, design system — traces back to decisions made here. This is the North Star.
+
+**Learn more:**
+- WDS Course Module 04: Product Brief — Your Strategic Foundation
+- WDS Course Module 05: Platform Requirements
+
+---
+
+## For Agents
+
+**Workflow:** `skill:wds-1-project-brief`
+**Agent trigger:** `PB` (Saga)
+**Templates:** `./resources/wds-1-project-brief/templates/`
+
+**Before writing anything in this folder:**
+1. Load the workflow and follow its steps
+2. Use Dialog mode for discovery — ask questions, don't assume
+3. Read existing materials if the user has them (check `wds-project-outline.yaml`)
+
+**File naming:** Number all documents with a two-digit prefix: `01-product-brief.md`, `02-content-language.md`, etc. Platform Requirements is always last — it summarizes technical decisions that emerge from the strategic documents above. Update the Documents table below as each file is created.
+
+**Harm:** Producing a brief from assumptions instead of conversation. A brief that doesn't reflect the user's actual goals forces every later phase to build on a wrong foundation.
+
+**Help:** Asking the right questions, listening deeply, and documenting what the user actually said. A good brief makes every later decision easier.
+
+---
+
+## Documents
+
+_This section will be updated as documents are created during Phase 1._
+
+| # | Document | Status |
+|---|----------|--------|
+| 01 | Product Brief | Not started |
+| 02 | Platform Requirements | Not started |
+
+---
+
+_Created using Whiteport Design Studio (WDS) methodology_