fix: use getTagsProvider for all auto-labeling paths, allow suggestions without notebook

- app/api/ai/tags/route.ts: getAIProvider → getTagsProvider (was using
  embedding model instead of tags model for legacy tag generation)
- lib/ai/services/auto-label-creation.service.ts: same fix
- hooks/use-auto-tagging.ts: remove notebookId gate that blocked all
  suggestions in "General Notes" — the API has a legacy path for this
- app/actions/admin-settings.ts: revalidateTag → updateTag (Next.js 16
  requires 2 args for revalidateTag)

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

memento-note/lib/ai/services/auto-label-creation.service.ts

@@ -1,5 +1,5 @@
 import { prisma } from '@/lib/prisma'
-import { getAIProvider } from '@/lib/ai/factory'
+import { getTagsProvider } from '@/lib/ai/factory'
 import { getSystemConfig } from '@/lib/config'
 
 export interface SuggestedLabel {
@@ -106,7 +106,7 @@ export class AutoLabelCreationService {
 
     try {
       const config = await getSystemConfig()
-      const provider = getAIProvider(config)
+      const provider = getTagsProvider(config)
       const response = await provider.generateText(prompt)
 
       // Parse AI response