Fix AI tagging issues and improve error messages

- Fall back to ai_enabled setting if ai_tagging_enabled not set
- Check both tags array and projectTags relationship for untagged projects
- Add detailed logging for debugging
- Show errors in toast instead of just counts
- Handle "no projects to tag" case with appropriate message
- Add early checks for OpenAI config and available tags

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/(admin)/admin/projects/page.tsx

@@ -252,9 +252,16 @@ export default function ProjectsPage() {
   // AI batch tagging mutation
   const batchTagProjects = trpc.tag.batchTagProjects.useMutation({
     onSuccess: (result) => {
-      toast.success(
-        `AI Tagging complete: ${result.processed} tagged, ${result.skipped} skipped, ${result.failed} failed`
-      )
+      if (result.errors && result.errors.length > 0) {
+        // Show first error if there are any
+        toast.error(`AI Tagging issue: ${result.errors[0]}`)
+      } else if (result.processed === 0 && result.skipped === 0 && result.failed === 0) {
+        toast.info('No projects to tag - all projects in this round already have tags')
+      } else {
+        toast.success(
+          `AI Tagging complete: ${result.processed} tagged, ${result.skipped} skipped, ${result.failed} failed`
+        )
+      }
       setAiTagDialogOpen(false)
       setSelectedRoundForTagging('')
       utils.project.list.invalidate()