Keep leases alive during long restores and exports; PR review fixes

Full restore, raw directory restore, per-user export and the safety export
held a fixed-TTL lease on the location that nothing refreshed. A restore or
export running longer than that TTL let a cleanup take over and delete data
still in use. They now refresh the lease while they work (per blob, per row
batch, per written chunk), throttled to once a minute.

Also:
- backup:prune still applies snapshot retention when user-export retention
  fails for a location.
- The recovery kit carries the deletion delay, so a disaster recovery keeps
  the original protection instead of falling back to 7 days. Older kits
  still import with the default.
- CI checkouts no longer persist the token in the git config.
- recoveryKit() has its real return type; the stale baseline entry is gone.

lib/UserMigration/RepositoryExportDestination.php

@@ -28,6 +28,8 @@ final class RepositoryExportDestination implements IExportDestination {
 	public function __construct(
 		private Repository $repo,
 		private string $uid,
+		/** Called while data is written (per chunk), to keep the location lease alive. */
+		private ?\Closure $heartbeat = null,
 	) {
 		$this->exportId = gmdate('Ymd\THis\Z') . '-' . bin2hex(random_bytes(4));
 	}
@@ -36,6 +38,7 @@ final class RepositoryExportDestination implements IExportDestination {
 		$writer = $this->repo->blobWriter($this->stats);
 		$writer->write($content);
 		$this->entries[self::norm($path)] = ['t' => 'f', 'b' => $writer->finish(), 's' => strlen($content)];
+		$this->beat();
 	}
 
 	public function addFileAsStream(string $path, $stream): void {
@@ -46,6 +49,7 @@ final class RepositoryExportDestination implements IExportDestination {
 				throw new UserMigrationException('Read error while exporting ' . $path);
 			}
 			$writer->write($chunk);
+			$this->beat();
 		}
 		$this->entries[self::norm($path)] = ['t' => 'f', 'b' => $writer->finish(), 's' => $writer->bytes()];
 	}
@@ -92,6 +96,12 @@ final class RepositoryExportDestination implements IExportDestination {
 		return $this->stats;
 	}
 
+	private function beat(): void {
+		if ($this->heartbeat !== null) {
+			($this->heartbeat)();
+		}
+	}
+
 	private static function norm(string $path): string {
 		return trim($path, '/');
 	}