UI_ShowClockPage()/UI_ShowSetTimePage() now take weekday/day/month(/year)
and build the date bar dynamically via Build_DateString() instead of
the fixed placeholder string. app_home.c reads the full date from RTC
via PCF8563_ReadDateTime() and recalculates weekday since the RTC's
stored date may differ from the software clock's. config.h exposes
current_day/month/year/weekday alongside the existing time fields so
main.c's debug commands don't need a separate include.
UI_ShowSetTimePage() cleared and redrew the entire screen on every
500ms blink toggle and on every up/down value change, causing a
full-screen flash instead of just the intended hour/minute digit
blinking. Split out UI_UpdateSetTimeDigit() which only repaints the
32x32px digit region for the field being edited; the full page draw
is now only used on entry. Field-switch (long-press CONFIRM) refreshes
both digit regions to clear any stale blanked-out state.
