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.

src/fenris/status_composition.py

@@ -17,11 +17,11 @@ from typing import Any, Dict, List, Optional
 # Status poll interval (AC78-6): lightweight 5s systemctl show poll
 STATUS_POLL_INTERVAL_S = 5
 
+from .timefmt import freshness_age_human
 from .status import (
     FRESH_THRESHOLD_S,
     STALENESS_THRESHOLD_S,
     grade_freshness,
-    freshness_age_human,
     is_deliberately_paused,
     monitoring_continuity,
     deliberate_pause_lines,