Add individual salary deposit agent tool

backend/app/agent/agent.py

@@ -35,6 +35,9 @@ How to answer:
   "ayer", "el martes", a specific date) need get_daily_spending with that
   day's bounds — cycle or category summaries have NO per-day data, so never
   answer a day question from them.
+- For a question about a specific salary deposit or its amount (including
+  "cuánto recibí hoy"), call get_salary_deposits with the relevant date range;
+  get_salary_summary is aggregate-only and cannot answer it.
 - Answer like an analyst, not a calculator. An aggregate number on its own
   is not an answer — show what it is made of, right away, without waiting
   to be asked: