Fix number of new replies to "own contributions"

Currently the "Own contributions" card at the top of the Q & A start screen always states "No new answers".

I can provide an additional field in GET /questions/categories if you want. I just need to know what the number is supposed to represent exactly. My guess right now would be the number of new replies to questions you posted in the last 24 hours. Maybe you can clarify, @mlbn33. :)

Marwin:
Die Anzahl der Antworten = (letzten 24h) die Antworten auf "eigene erstelle Fragen"

Related backend issue: tc-server#97 (closed)