chore: remove vibe-coding artifacts from tracking, sync notes and obsidian config

- Untrack .claude/launch.json (Claude Code config)
- Add .claude/, .mcp.json, CLAUDE.md, and AI-generated CSVs to .gitignore
- Add _notes/ vault (architecture, API, tasks, bugs, infra docs)
- Add .obsidian/ plugin/vault config (workspace state excluded)
- Sync CHANGELOG.md

_notes/07 - Design & UI/Design Notes.md

@@ -0,0 +1,30 @@
+# Design & UI Notes
+
+## Theme
+- Dark/Light mode supported via `ThemeManager` (`lib/core/theme_manager.dart`)
+- SVG assets rendered via `flutter_svg`
+
+## Responsive Layout
+- `responsive_layout.dart` switches between mobile and desktop layouts
+- Breakpoints: > document exact breakpoint values
+
+## Color Palette
+> Add primary, secondary, background, accent colors here
+
+## Typography
+> Document font families and text styles used
+
+## Component Library
+> Notable reusable widgets in `lib/widgets/`
+
+| Widget | File | Purpose |
+|--------|------|---------|
+| | | |
+
+## Assets
+- Images: `assets/images/`
+- Fonts: `assets/fonts/`
+- Videos: `assets/videos/` (large files, git-ignored)
+- SVGs: used inline via `flutter_svg`
+
+## Notes