refactor: migrate DataExportSection to PlatformServiceMixin

- Use PlatformServiceMixin for platform and database access
- Replace manual PlatformService instantiation with mixin methods/properties
- Use $contacts() for contact export
- Use capabilities for platform checks in template and logic
- Remove unused imports and redundant code
- Lint clean

src/components/RegistrationNotice.vue

@@ -7,7 +7,8 @@
     aria-live="polite"
   >
     <p class="mb-4">
-      Before you can publicly announce a new project or time commitment, a friend needs to register you.
+      Before you can publicly announce a new project or time commitment, a
+      friend needs to register you.
     </p>
     <button
       class="inline-block text-md bg-gradient-to-b from-blue-400 to-blue-700 shadow-[inset_0_-1px_0_0_rgba(0,0,0,0.5)] text-white px-4 py-2 rounded-md"
@@ -19,14 +20,14 @@
 </template>
 
 <script lang="ts">
-import { Component, Vue, Prop, Emit } from 'vue-facing-decorator';
+import { Component, Vue, Prop, Emit } from "vue-facing-decorator";
 
-@Component({ name: 'RegistrationNotice' })
+@Component({ name: "RegistrationNotice" })
 export default class RegistrationNotice extends Vue {
   @Prop({ required: true }) isRegistered!: boolean;
   @Prop({ required: true }) show!: boolean;
 
-  @Emit('share-info')
+  @Emit("share-info")
   shareInfo() {}
 }
-</script> 
+</script>