Refactor error handling in FalukantService and enhance user feedback in HealthView

- Changed error throwing in FalukantService to use PreconditionError for better clarity.
- Added translations for "too close" error in both German and English locales.
- Improved user feedback in HealthView by displaying error messages in a dialog upon measure execution failure.

frontend/src/views/falukant/HealthView.vue

@@ -129,13 +129,22 @@ export default {
         async performMeasure() {
             if (!this.selectedMeasure) return;
             try {
-                await apiClient.post('/api/falukant/health', {
+                const { data } = await apiClient.post('/api/falukant/health', {
                     measureTr: this.selectedTr
                 });
+                // Feedback via global message dialog
+                const title = this.$t('falukant.healthview.title');
+                const body = data?.delta != null
+                    ? `${this.$t(`falukant.healthview.measures.${this.selectedTr}`)}: ${data.delta > 0 ? '+' : ''}${data.delta}`
+                    : this.$t('message.success');
+                this.$root.$refs.messageDialog?.open(body, title);
                 await this.loadHealthData();
                 this.selectedTr = '';
             } catch (err) {
                 console.error('Error performing measure', err);
+                const title = this.$t('falukant.healthview.title');
+                const remoteMsg = err?.response?.data?.error || err?.message || String(err);
+                this.$root.$refs.messageDialog?.open(remoteMsg, title);
             }
         },
         handleDaemonMessage(evt) {