Feature/refactor dark theme css selector (#3662)

* Refactor dark theme CSS selector

* Update changelog

libs/ui/src/lib/activities-filter/activities-filter.component.scss

@@ -15,7 +15,7 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   .mat-mdc-form-field {
     color: rgba(var(--light-primary-text));
   }

libs/ui/src/lib/activity-type/activity-type.component.scss

@@ -40,7 +40,7 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   .activity-type-badge {
     background-color: rgba(var(--palette-foreground-text-dark), 0.1) !important;
   }

libs/ui/src/lib/assistant/assistant-list-item/assistant-list-item.scss

@@ -10,7 +10,7 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   &.has-focus {
     a {
       color: rgba(var(--dark-primary-text));

libs/ui/src/lib/assistant/assistant.scss

@@ -26,7 +26,7 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   .date-range-selector-container {
     border-color: rgba(var(--light-dividers));
   }

libs/ui/src/lib/fire-calculator/fire-calculator.component.scss

@@ -25,7 +25,7 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   ::ng-deep {
     .mdc-text-field--disabled {
       .mdc-notched-outline__leading,

libs/ui/src/lib/no-transactions-info/no-transactions-info.component.scss

@@ -11,6 +11,6 @@
   }
 }
 
-:host-context(.is-dark-theme) {
+:host-context(.theme-dark) {
   border-color: rgba(var(--light-dividers));
 }