refactor(tui): extract Activity readout and show local time

Move activity data assembly out of tui.py into activity_readout, behind
readout(conn, selection, now). Dashboard and fenris-monitor enable now show
local time with a timezone label, inspected points keep a secondary UTC line,
and the legacy UTC-relabelled day and hour branches are gone. Time formatting
(including freshness_age_human) lives in timefmt. Hour offsets now render as
+05:30 to match day labels.

tests/test_status.py

@@ -25,7 +25,6 @@ sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
 
 from fenris.status import (
     grade_freshness,
-    freshness_age_human,
     format_disclosures,
     check_retired_command,
     check_retired_flag,
@@ -36,6 +35,7 @@ from fenris.status import (
 )
 from fenris.store import init_store, SCHEMA_VERSION
 from fenris.projection import DISCLOSURES, ConfidenceState
+from fenris.timefmt import freshness_age_human
 
 
 # ---------------------------------------------------------------------------