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_local_day.py

@@ -624,6 +624,7 @@ class TestCollectorIntegration:
             assert summary["activity_state"] in ("incomplete", "so_far")
         conn.close()
 
+        from fenris.activity_readout import selected_local_day
         from fenris.status import read_status
         from fenris.tui import FenrisTuiApp
 
@@ -634,7 +635,9 @@ class TestCollectorIntegration:
                 Path(store), second_at, query_services=False
             ) as (reader, _):
                 assert reader is not None
-                app._render_local_day(reader)
+                app._render_local_day(*selected_local_day(
+                    reader, app._activity_selection, second_at,
+                ))
             visible = str(app.query_one("#local-day").render())
             assert "2026-09-02" in visible
             assert "Asia/Kolkata +05:30" in visible