Add history view with day-grouped transaction list

Month navigation with prev/next buttons, transactions grouped by date
with headers (Today/Yesterday/formatted date), category icons, amounts
color-coded green for income and red for expenses, and daily net totals.

outlay-gtk/src/main.rs

@@ -1,3 +1,4 @@
+mod history_view;
 mod log_view;
 mod window;