M5: deletion delay with trash, passphrase slots, ransomware documentation

- removed snapshots go to a trash on the location and their data is only
  freed after the deletion delay, which is chosen when the key is created
  (default 7 days, 1-365) and cannot be changed afterwards; any admin can
  bring them back (occ backup:trash, backup:trash:restore, web UI)
- up to three passphrase slots open the same master key (like LUKS), so
  one person leaving or dying does not lock the company out; slot changes
  are written to every location, announced to all admins and require a
  new recovery kit confirmation, while backups keep running
- occ backup:key:slots, backup:key:slot:add|replace|remove; key init takes
  --label and --delete-delay-days
- web UI: deletion delay and first slot at key creation, slot management,
  trash per location with restore; all behind password confirmation
- README: key, slots (safe / CTO / head of IT), and protection against
  ransomware: object lock in compliance mode (e.g. 90 days), credentials
  without delete rights, provider snapshots, off-site copy

src/api.js

@@ -17,7 +17,12 @@ async function call(method, path, data) {
 
 export default {
 	status: () => call('get', '/status'),
-	initKey: (passphrase) => call('post', '/key', { passphrase }),
+	initKey: (passphrase, deleteDelayDays, label) => call('post', '/key', { passphrase, deleteDelayDays, label }),
+	addSlot: (passphrase, label) => call('post', '/key/slots', { passphrase, label }),
+	replaceSlot: (slot, passphrase, label) => call('put', `/key/slots/${slot}`, { passphrase, label }),
+	removeSlot: (slot) => call('delete', `/key/slots/${slot}`),
+	trash: (targetId) => call('get', `/targets/${targetId}/trash`),
+	untrash: (targetId, snapshotId) => call('post', `/targets/${targetId}/trash/${snapshotId}`),
 	kitUrl: () => url('/key/kit'),
 	confirmKit: (accepted, phrase) => call('post', '/key/confirm', { accepted, phrase }),
 	backends: () => call('get', '/backends'),