Update 22: Indexer reorg-safety report on the status page

Sometimes a blockchain briefly replaces its latest few blocks with a different version. This is called a reorganisation, and the indexer is built to detect it and rewind safely. The status page now reports how it is coping: how many reorganisations it has handled, the deepest one, and when it last checked. If one were ever too deep to repair automatically, the page would say so plainly.