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_monitor.py

@@ -84,6 +84,25 @@ class TestEnableIdempotentMatrix:
         assert cursor.fetchone() is not None
         conn.close()
 
+    def test_enable_reports_period_start_in_local_time(
+        self, store_path, monkeypatch, capsys,
+    ):
+        """The opened-at message is local time with its timezone label."""
+        monkeypatch.setenv("TZ", "Asia/Kolkata")
+        args = MagicMock(now=True, store_path=store_path)
+        conn = init_store(store_path)
+        conn.execute("DELETE FROM monitoring_periods")
+        conn.commit()
+        conn.close()
+
+        with patch("fenris.monitor.enable_timer"):
+            cmd_enable(args)
+
+        out = capsys.readouterr().out
+        assert "Monitoring period opened at" in out
+        assert "Asia/Kolkata +05:30" in out
+        assert "+00:00" not in out
+
     def test_resume_with_open_period_noop(self, store_path):
         """Resume with open period: no-op (gap stays inside as unknown)."""
         # Initialize store and open a period