fix(import): persist object_key + metadata; add nav + logout session cleanup

- Import task: persist object_key, author, cover_url, genres, summary,
  book_status in PocketBase so the runner can fetch the file and write
  book metadata on completion
- Runner poll mode: pass task.ObjectKey instead of empty string
- Runner: write BookMeta + UpsertBook in Meilisearch after chapter ingest
  so imported books appear in catalogue and search
- Import UI: add author, cover URL, genres, summary, status fields; add
  AI tasks panel (chapter names, description, image gen, tagline) after
  import completes; add AI tasks button on each done task in the list
- Admin nav: add Notifications entry to sidebar (all 5 locales)
- Logout: delete user_sessions row on sign-out so sessions don't
  accumulate as phantoms after each login/logout cycle

backend/internal/asynqqueue/producer.go

@@ -7,6 +7,7 @@ import (
 	"log/slog"
 
 	"github.com/hibiken/asynq"
+	"github.com/libnovel/backend/internal/domain"
 	"github.com/libnovel/backend/internal/taskqueue"
 )
 
@@ -88,18 +89,18 @@ func (p *Producer) CreateTranslationTask(ctx context.Context, slug string, chapt
 }
 
 // CreateImportTask creates a PocketBase record then enqueues an Asynq job for PDF/EPUB import.
-func (p *Producer) CreateImportTask(ctx context.Context, slug, title, fileType, objectKey, initiatorUserID string) (string, error) {
-	id, err := p.pb.CreateImportTask(ctx, slug, title, fileType, objectKey, initiatorUserID)
+func (p *Producer) CreateImportTask(ctx context.Context, task domain.ImportTask) (string, error) {
+	id, err := p.pb.CreateImportTask(ctx, task)
 	if err != nil {
 		return "", err
 	}
 
 	payload := ImportPayload{
 		PBTaskID:  id,
-		Slug:      slug,
-		Title:     title,
-		FileType:  fileType,
-		ObjectKey: objectKey,
+		Slug:      task.Slug,
+		Title:     task.Title,
+		FileType:  task.FileType,
+		ObjectKey: task.ObjectKey,
 	}
 	if err := p.enqueue(ctx, TypeImportBook, payload); err != nil {
 		// Non-fatal: PB record exists; runner will pick it up on next poll.