Three interrelated fixes for the HTTP SSE endpoint:
1. **SignalAccountFiles** — Replace ACI.parseOrThrow() with UUID-string
lookup from accountsStore.getAllAccounts(). The old approach failed when
a raw UUID string (from URL query param) was passed. Added
getAccountNumberByAci() helper to reduce duplication.
2. **MultiAccountManagerImpl** — Catch IllegalArgumentException in
getManager() for both phone number and ACI lookup paths. Also check if
the UUID corresponds to an already-loaded manager before trying to
initByAci(), preventing OverlappingFileLockException when SSE requests
arrive with a UUID for an account that was loaded at startup.
3. **Util.getQueryMap()** — Preserve '+' characters in query parameter
values by escaping them before URLDecoder.decode(). Without this,
URLDecoder converts '+' to space, breaking phone numbers like
'+4915422389' which become ' 4915422389'.
* Initial version of SharedContacts from data message. Need to change location of avatar downloaded and fix plain text mode
* Made empty strings for json null and fixed plaintext output
* Removed old comments, simplified if-statement and added a 'leadingSpaces' field to the print attachments/mentions functions
* Added AsamK's changes
