style: Adjust button themes for improved contrast and consistency

This commit refactors the button theme overrides to enhance visual styling, particularly for dark mode. Changes focus on adjusting background colors, border colors, and text/icon colors to improve contrast and create a more consistent look across different button states.

### Key Changes:

*   **Primary Outlined Button (Dark Mode):**
    *   The default state now has a transparent background (`Colors.gray.withAlpha(0)`) for a ghost-like appearance.
    *   The default border color is now `Colors.gray[200]`.
    *   The hovered background color has been darkened from `gray[300]` to `gray[600]`.
    *   Text and icon colors have been changed from `Colors.black` to `Colors.gray[200]` to ensure readability on the new darker backgrounds.

*   **Destructive (Red) Button:**
    *   The border color for default and hovered states is now unified to `Colors.red[600]`.
    *   The text and icon colors have been adjusted from `Colors.white` to `Colors.gray[100]` for a slightly softer appearance.

Author: Lukas Gundermann

lib/screens/widgets/overrides/button_themes.dart

@@ -23,25 +23,31 @@ class ButtonThemes extends StatelessWidget {
             );
           } else if (states.contains(WidgetState.hovered)) {
             return defaultDecoration.copyWithIfBoxDecoration(
-              color: isDark ? Colors.gray[300] : Colors.gray[200],
+              color: isDark ? Colors.gray[600] : Colors.gray[200],
               border: Border.all(
                 color: isDark ? Colors.blue[300] : Colors.blue[600],
               ),
             );
           } else {
             return defaultDecoration.copyWithIfBoxDecoration(
-              color: isDark ? Colors.gray[400] : Colors.gray[100],
+              color: isDark
+                  ? Colors.gray.withAlpha(0)
+                  : Colors.white.withAlpha(0),
               border: Border.all(
-                color: isDark ? Colors.blue[100] : Colors.blue[900],
+                color: isDark ? Colors.gray[200] : Colors.blue[900],
               ),
             );
           }
         },
         textStyle: (context, states, defaultTextStyle) {
-          return defaultTextStyle.copyWith(color: isDark ? Colors.black : Colors.blue[900]);
+          return defaultTextStyle.copyWith(
+            color: isDark ? Colors.gray[200] : Colors.blue[900],
+          );
         },
         iconTheme: (context, states, defaultIconTheme) {
-          return defaultIconTheme.copyWith(color: isDark ? Colors.black : Colors.blue[900]);
+          return defaultIconTheme.copyWith(
+            color: isDark ? Colors.gray[200] : Colors.blue[900],
+          );
         },
       ),
       child: ComponentTheme(
@@ -56,14 +62,20 @@ class ButtonThemes extends StatelessWidget {
                 color: isDark ? Colors.gray[300] : Colors.gray[200],
               );
             } else {
-              return defaultDecoration.copyWithIfBoxDecoration(color: isDark ? Colors.gray[400] : Colors.gray[100]);
+              return defaultDecoration.copyWithIfBoxDecoration(
+                color: isDark ? Colors.gray[400] : Colors.gray[100],
+              );
             }
           },
           textStyle: (context, states, defaultTextStyle) {
-            return defaultTextStyle.copyWith(color: isDark ? Colors.black : Colors.blue[900]);
+            return defaultTextStyle.copyWith(
+              color: isDark ? Colors.black : Colors.blue[900],
+            );
           },
           iconTheme: (context, states, defaultIconTheme) {
-            return defaultIconTheme.copyWith(color: isDark ? Colors.black : Colors.blue[900]);
+            return defaultIconTheme.copyWith(
+              color: isDark ? Colors.black : Colors.blue[900],
+            );
           },
         ),
         child: ComponentTheme(
@@ -109,20 +121,20 @@ class ButtonThemes extends StatelessWidget {
                 } else if (states.contains(WidgetState.hovered)) {
                   return defaultDecoration.copyWithIfBoxDecoration(
                     color: Colors.red[700],
-                    border: Border.all(color: Colors.red[700]),
+                    border: Border.all(color: Colors.red[600]),
                   );
                 } else {
                   return defaultDecoration.copyWithIfBoxDecoration(
                     color: Colors.red[500],
-                    border: Border.all(color: Colors.red[700]),
+                    border: Border.all(color: Colors.red[600]),
                   );
                 }
               },
               textStyle: (context, states, defaultTextStyle) {
-                return defaultTextStyle.copyWith(color: Colors.white);
+                return defaultTextStyle.copyWith(color: Colors.gray[100]);
               },
               iconTheme: (context, states, defaultIconTheme) {
-                return defaultIconTheme.copyWith(color: Colors.white);
+                return defaultIconTheme.copyWith(color: Colors.gray[100]);
               },
             ),
             child: ComponentTheme(