feat: Implement Dark Mode

Added styles and configurations to enable dark mode throughout the application. The dark mode features a deep blue color scheme for primary elements and improved visibility for cursor. Selected option text in mat-select now appears in white for better contrast. This enhancement provides users with the option to switch between light and dark modes seamlessly.

Changes:
- Added dark mode styles in the theme service
- Updated mifosx-theme.scss for dark mode customization
- Adjusted cursor visibility in dark mode
- Modified selected option text color in mat-select

Fixes #2021

Implemented the black-logo image into white-logo-image dynamically

src/theme/_material-palette.scss

@@ -1,3 +1,6 @@
+
+/* ############ Light mode palettes ################*/
+
 $primary-palette: (
   100: #5ba2ec,
   500: #1074b9,
@@ -19,3 +22,27 @@ $accent-palette: (
     700: rgba(black, 0.87)
   )
 );
+
+/* ############ Dark mode palettes ################*/
+
+$dark-primary-palette: (
+  100: #273350,
+  500: #313f6b,
+  700: #39415c,
+  contrast: (
+    100: white,
+    500: rgba(white, 0.87),
+    700: rgba(white, 0.87)
+  )
+);
+
+$dark-accent-palette: (
+  100: #364461,
+  500: #3e5372,
+  700: #476385,
+  contrast: (
+    100: white,
+    500: white,
+    700: white
+  )
+);