feat(settings): add mpvReuseInstance setting to store and i18n

Add MPV_REUSE_INSTANCE key to the electron backend store service and
include mpvReuseInstance in the shared settings interface so the new
boolean setting is persisted and available across renderer and main
processes.

Also update English i18n JSON formatting and expand the HOME section
translations (reformatting and adding nested playlist-related keys)
to ensure the UI strings remain consistent after changes.

apps/web/src/app/settings/settings.component.html

@@ -128,6 +128,23 @@
                     </mat-form-field>
                 </div>
             </div>
+            <div class="row">
+                <div class="column">
+                    {{ 'SETTINGS.MPV_REUSE_INSTANCE_LABEL' | translate }}
+                    <p>
+                        {{
+                            'SETTINGS.MPV_REUSE_INSTANCE_DESCRIPTION'
+                                | translate
+                        }}
+                    </p>
+                </div>
+                <div class="column margin-right">
+                    <mat-checkbox
+                        class="column"
+                        formControlName="mpvReuseInstance"
+                    ></mat-checkbox>
+                </div>
+            </div>
         }
         @if (settingsForm.value.player === 'vlc') {
             <div class="row">