feat(timeago): add format_time_html returning a <time> element

Wrap humanize_delta in an HTML <time> element with datetime= and
title= attributes carrying the precise UTC value, so hovering surfaces
the exact timestamp regardless of the relative label.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

l4d2web/l4d2web/services/timeago.py

@@ -1,5 +1,7 @@
 from datetime import UTC, datetime
 
+from markupsafe import Markup, escape
+
 
 _MONTHS = (
     "Jan", "Feb", "Mar", "Apr", "May", "Jun",
@@ -51,3 +53,18 @@ def humanize_delta(then: datetime, now: datetime | None = None) -> str:
         return _format_date(then, now)
 
     return _relative_label(abs_seconds, past=(delta_seconds > 0))
+
+
+def format_time_html(then: datetime, now: datetime | None = None) -> Markup:
+    if now is None:
+        now = datetime.now(UTC)
+    then_utc = _ensure_utc(then).astimezone(UTC)
+    now = _ensure_utc(now)
+
+    label = humanize_delta(then_utc, now=now)
+    iso = then_utc.isoformat()
+    title = then_utc.strftime("%Y-%m-%d %H:%M:%S UTC")
+    return Markup(
+        f'<time datetime="{escape(iso)}" title="{escape(title)}">'
+        f"{escape(label)}</time>"
+    )

l4d2web/tests/test_timeago.py

@@ -1,8 +1,9 @@
 from datetime import UTC, datetime, timedelta
 
 import pytest
+from markupsafe import Markup
 
-from l4d2web.services.timeago import humanize_delta
+from l4d2web.services.timeago import format_time_html, humanize_delta
 
 
 NOW = datetime(2026, 5, 16, 12, 0, 0, tzinfo=UTC)
@@ -82,3 +83,35 @@ def test_humanize_delta_year_boundary_includes_year_when_years_differ():
     now = datetime(2026, 1, 15, 12, 0, 0, tzinfo=UTC)
     then = datetime(2025, 11, 15, 12, 0, 0, tzinfo=UTC)
     assert humanize_delta(then, now=now) == "15 Nov 2025"
+
+
+def test_format_time_html_returns_markup():
+    then = NOW - timedelta(minutes=5)
+    out = format_time_html(then, now=NOW)
+    assert isinstance(out, Markup)
+
+
+def test_format_time_html_contains_time_element_with_attrs():
+    then = datetime(2026, 5, 16, 14, 32, 11, tzinfo=UTC)
+    now = then + timedelta(minutes=5)
+    out = str(format_time_html(then, now=now))
+    assert out.startswith("<time ")
+    assert out.endswith("</time>")
+    assert 'datetime="2026-05-16T14:32:11+00:00"' in out
+    assert 'title="2026-05-16 14:32:11 UTC"' in out
+    assert ">5 minutes ago<" in out
+
+
+def test_format_time_html_label_matches_humanize_delta():
+    then = NOW - timedelta(hours=2)
+    label = humanize_delta(then, now=NOW)
+    out = str(format_time_html(then, now=NOW))
+    assert f">{label}<" in out
+
+
+def test_format_time_html_normalises_naive_input_to_utc():
+    then_naive = datetime(2026, 5, 16, 14, 32, 11)
+    now = datetime(2026, 5, 16, 14, 37, 11, tzinfo=UTC)
+    out = str(format_time_html(then_naive, now=now))
+    assert 'datetime="2026-05-16T14:32:11+00:00"' in out
+    assert 'title="2026-05-16 14:32:11 UTC"' in out