Initial braindump app implementation

Create a complete braindump note-taking application with Dioxus 0.7 featuring:
- Note capture with title, content, and tags
- Full CRUD operations (create, read, update, delete)
- Search functionality for notes
- Tag-based filtering
- Note pinning for quick access
- Modern dark theme with purple accents
- Responsive sidebar layout
- Clean card-based note list
- Full-text editor with auto-save hint

Implemented with:
- Dioxus 0.7.1 fullstack for reactive UI and server functions
- Workspace pattern with shared API crate
- In-memory storage using LazyLock
- Server functions for note management

All core features working and ready for testing.

packages/web/assets/main.css

@@ -0,0 +1,6 @@
+body {
+    background-color: #0f1116;
+    color: #ffffff;
+    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
+    margin: 20px;
+}