style(ui): redesign app layout to native macOS density and refine visual theme

- Adjusted overall layout scale to perfectly match original native macOS density.

- Refined sidebar into a floating rounded slab with proper padding, border, and toggle button placement.

- Fixed drag region overlap preventing button interactions in the title bar.

- Removed artificial shadow lines and scrollbars from the sidebar.

- Updated Tauri backend configuration, dependencies, and scheduler functions for improved stability.

apps/desktop/src-tauri/Cargo.toml

@@ -18,7 +18,7 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = ["tray-icon", "image-png"] }
+tauri = { version = "2", features = ["macos-private-api", "tray-icon", "image-png"] }
 tauri-plugin-opener = "2"
 tauri-plugin-dialog = "2"
 serde = { version = "1", features = ["derive"] }
@@ -47,3 +47,4 @@ rusqlite = { version = "0.40.1", features = ["bundled"] }
 chrono = "0.4.38"
 cocoa = "0.25"
 objc = "0.2.7"
+window-vibrancy = "0.7.1"