feat: replace blinko with affine, route notifications to telegram

- Add AFFiNE stack (affine.pivoine.art): main app, migration job,
  redis, pgvector postgres
- Remove blinko stack
- Update backup.sh: swap blinko_db → affine_db
- Update README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_backup/backup.sh

@@ -33,7 +33,7 @@ mkdir -p "$DUMP_DIR"
 
 declare -A DATABASES=(
   [umami_db]="umami:umami"
-  [blinko_db]="blinko:blinko"
+  [affine_db]="affine:affine"
   [gitea_db]="gitea:gitea"
   [n8n_db]="n8n:n8n"
   [immich_db]="immich:immich"