feat: add Nepal flag SVG and update tray icon rendering for Windows

Introduced a compact Nepal flag SVG for the Windows tray icon, ensuring visibility against varying taskbar backgrounds. Updated the tray icon rendering logic to utilize the flag instead of displaying the date, while maintaining the ability to render the date for other platforms. Enhanced the icon rendering function to account for light and dark taskbar themes, ensuring appropriate color contrast for the digits. Added tests to verify the flag rendering and color adjustments based on the panel's light or dark state.

Author: adarshaacharya

Cargo.lock

@@ -36,6 +36,11 @@ tauri-plugin-process = "2"
 tokio = { version = "1", features = ["macros", "rt"] }
 tiny-skia = "0.11"
 cosmic-text = "0.14"
+# Renders the bundled Nepal flag SVG for Windows' tray icon. Pinned to 0.44 —
+# the last resvg release on tiny-skia 0.11, matching the pin above rather than
+# the 0.12 that newer resvg wants. `default-features = false` drops text/font
+# support (`usvg`'s "text" feature and friends): the flag has no text in it.
+resvg = { version = "0.44", default-features = false }
 
 [target."cfg(not(any(target_os = \"android\", target_os = \"ios\")))".dependencies]
 tauri-plugin-autostart = "2"