Each summary card (Einnahmen, Ausgaben, Saldo) now shows a trend line
comparing the current month to the previous one. The previous month's
summary is fetched in parallel via the existing /budget/summary endpoint,
so there is no extra round-trip latency. Positive deltas render in green
(▲), negative in red (▼), unchanged in neutral grey (—).
Closes BL-02.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Ulas