Fix recovery tests to use newer announcement timestamps

Recovery tests were failing because they re-sent the exact same event
after deletion. NIP-09 marks events as deleted by event ID, so re-sending
the same ID is rejected.

Real-world behavior: users create NEW events with NEWER timestamps when
re-publishing a deleted repository.

Changes:
- All recovery tests now create new announcements with different content
- Different content ensures newer created_at timestamps (different event IDs)
- Tests verify recovery works with proper event flow
- All 7 recovery tests now passing

This matches real-world usage patterns where users would naturally create
a new announcement event when re-publishing a repository.

tests/nip09_recovery.rs

@@ -747,7 +747,7 @@ async fn test_multiple_repositories_recovery() {
         .await
         .unwrap();
 
-    // Should have announcement1 and issue1
+    // Should have announcement1 and issue1 (and possibly issue2 if both were restored)
     assert!(
         events_after_first.len() >= 2,
         "Repo1 events should be restored"
@@ -763,7 +763,7 @@ async fn test_multiple_repositories_recovery() {
         .await
         .unwrap();
 
-    // Should have all 4 events
+    // Should have all 4 events: 2 announcements + 2 issues
     assert_eq!(
         events_after_second.len(),
         4,