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/suno-feedback-elicitor/references/headless-contract.md

@@ -0,0 +1,34 @@
+# Headless Output Contract
+
+```json
+{
+  "feedback_analysis": {
+    "triage_type": "clear|positive|vague|contradictory|technical",
+    "identified_dimensions": ["vocals", "energy"],
+    "confidence": "high|medium|low"
+  },
+  "adjustment_recommendations": {
+    "style_prompt": {"add": [], "remove": [], "reorder_notes": ""},
+    "exclusions": {"add": [], "remove": []},
+    "sliders": {"weirdness": "", "style_influence": ""},
+    "lyrics": {"changes": []},
+    "model_suggestion": "",
+    "studio_features": []
+  },
+  "confidence_scores": {"style_prompt": "high", "sliders": "medium"},
+  "iteration_log": {"session_id": "", "round": 1, "tried": [], "user_reaction": "", "reasoning_chain": ""},
+  "suggested_next_action": {"skill": "", "mode": "", "params": {}}
+}
+```
+
+## Headless Input Contract
+
+| Flag | Required | Description |
+|------|----------|-------------|
+| `--feedback` | Yes | Text string or JSON with feedback content |
+| `--style-prompt` | Recommended | Original style prompt used for generation |
+| `--model` | Optional | Suno model used (v4.5-all, v4 Pro, v4.5 Pro, v4.5+ Pro, v5 Pro, v5.5 Pro) |
+| `--sliders` | Optional | JSON with Weirdness/StyleInfluence values |
+| `--lyrics` | Optional | File path to original lyrics |
+| `--band-profile` | Optional | Profile name for context loading |
+| `--iteration-log` | Optional | File path to previous round's iteration log |