A saved Immich server is a node on the column beside the drives: no handle,
no picker — the key lives on the backend and the page only ever calls
`/api/immich/*` on its own origin. The dialog takes the address, the name and
the key, checks the key before storing anything, and offers the albums the key
can see; a blank tick list and a blank id field both mean every album. A share
key is one album and so has no picker.
`syncImmich` turns a server's albums into the shapes the tree already draws —
rows in `photos`, names in `walked` — so the column, the wall and the strip
need nothing new. The node's menu is the disk's menu minus what a server has
no disk for.
Also fixes `saveWalkedDirs` filling its noughts in before folding the keys:
a reading that spelled its keys the way it found them (a server's album
labels) had the lower-case spelling of a counted key written in as nought,
and the fold that settles the two spellings kept the nought.
