fix: address coderabbit round 3 — reactivity, a11y, user feedback

- Use getter function with until() for Pinia store reactivity (useErrorReport)
- Set alt="" on decorative thumbnail images (MissingMediaLibrarySelect)
- Show toast on unsupported file type instead of silent return

src/components/rightSidePanel/errors/useErrorReport.ts

@@ -48,7 +48,7 @@ export function useErrorReport(cardSource: MaybeRefOrGetter<ErrorCardData>) {
 
       if (!systemStatsStore.systemStats) {
         if (systemStatsStore.isLoading) {
-          await until(systemStatsStore.isLoading).toBe(false)
+          await until(() => systemStatsStore.isLoading).toBe(false)
         } else {
           try {
             await systemStatsStore.refetchSystemStats()

src/platform/missingMedia/components/MissingMediaLibrarySelect.vue

@@ -52,7 +52,7 @@
             <img
               v-if="mediaType === 'image'"
               :src="getPreviewUrl(option.value)"
-              :alt="option.name"
+              alt=""
               class="size-8 shrink-0 rounded-sm object-cover"
               loading="lazy"
             />

src/platform/missingMedia/composables/useMissingMediaInteractions.ts

@@ -138,7 +138,15 @@ export function useMissingMediaInteractions() {
         : mediaType === 'video'
           ? 'video/'
           : 'image/'
-    if (!file.type || !file.type.startsWith(expectedPrefix)) return
+    if (!file.type || !file.type.startsWith(expectedPrefix)) {
+      useToastStore().addAlert(
+        st(
+          'toastMessages.unsupportedFileType',
+          'Unsupported file type. Please select a valid file.'
+        )
+      )
+      return
+    }
 
     store.uploadState[name] = { fileName: file.name, status: 'uploading' }