Without system cron: warning and a backup that moves on while the page is open (#13); progress of the database phase; Bin tab

- The admin page and backup:status warn when background jobs do not run on a
  system cron, or the cron stopped, with a link to how to set one up.
- Without a working system cron, the open admin page moves a running backup
  forward through /api/tick, a short step per poll.
- The database phase shows the tables dumped ("db: 47/183 tables"); a backup
  that has not moved for 15 minutes says it is waiting for background jobs.
- The trash of restore points is on a tab of its own, Bin.
- New screenshots; changelog and plan for 1.0.2.

lib/Job/BackupRun.php

@@ -176,12 +176,12 @@ final class BackupRun {
 	}
 
 	/**
-	 * progress() of a run, while it is in its files phase.
+	 * progress() of a run in its files phase; in its database phase, the tables dumped so far.
 	 *
-	 * @return array{fraction: float, approximate: bool}|null
+	 * @return array{fraction: float, approximate: bool, tables?: int, totalTables?: int}|null
 	 */
 	public static function progressOf(\OCA\NgBackup\Db\Run $run): ?array {
-		if ($run->getStatus() !== \OCA\NgBackup\Db\Run::RUNNING || $run->getPhase() !== 'files') {
+		if ($run->getStatus() !== \OCA\NgBackup\Db\Run::RUNNING || !in_array($run->getPhase(), ['db', 'files'], true)) {
 			return null;
 		}
 		try {
@@ -189,6 +189,14 @@ final class BackupRun {
 		} catch (\JsonException) {
 			return null;
 		}
+		if ($run->getPhase() === 'db') {
+			// Tables dumped so far, as of the last step (none known before the first step ends)
+			$tables = count($state['dump']['tables'] ?? []);
+			return $tables > 0
+				? ['fraction' => min(1.0, ($state['dump']['i'] ?? 0) / $tables), 'approximate' => false,
+					'tables' => (int)($state['dump']['i'] ?? 0), 'totalTables' => $tables]
+				: null;
+		}
 		return is_array($state['files'] ?? null) ? self::progress($state['files']) : null;
 	}