[Server/Client/Protocol] Address developer role review feedback

Address ZeizaZach's review of the developer staff role:

- Nudge the developer log query to exclude private chat and sender IPs
  (the ModeratorCommand path still sees everything).
- Deduplicate Command_GetLogHistory into Command_ViewLogHistory, which now
  extends both ModeratorCommand (ext) and DeveloperCommand (dev_ext); the
  client picks the DeveloperCommand-scoped extension by extendee, and the
  server reads it via the extension number.
- Pull the uptime snapshot SQL into Servatrice_DatabaseInterface as
  getLatestUptimeSnapshot() and widen the reported counters to 64-bit.
- Document the admin bitfield (1 admin, 2 moderator, 4 judge, 8 developer)
  and add a server-side test for the developer command path.

cockatrice/src/interface/widgets/tabs/tab_developer.cpp

@@ -94,7 +94,7 @@ void TabDeveloper::refreshClicked()
 void TabDeveloper::serverStatsResponse(const Response &resp)
 {
     if (resp.response_code() != Response::RespOk) {
-        statusLabel->setText(tr("Failed to collect server statistics."));
+        statusLabel->setText(tr("No server statistics available yet."));
         return;
     }