fix(activities): reject malformed NIP-52 kind 31922 events at parse time

parseCalendarDateEvent accepted any non-empty `start` string, letting
events with embedded times (e.g. "2026-05-25T10:00") through. Downstream
parseIsoDate then split on "-" and produced an Invalid Date, crashing
the renderer with "RangeError: Invalid time value".

Validate `start` and `end` against YYYY-MM-DD at parse time so bad events
are dropped before reaching the view — symmetric with how the time-event
parser rejects unparseable timestamps.

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

src/modules/activities/types/nip52.ts

@@ -181,6 +181,14 @@ export function parseCalendarDateEvent(event: NostrEvent): CalendarDateEvent | n
 
   if (!dTag || !title || !start) return null
 
+  // NIP-52 kind 31922 requires YYYY-MM-DD. Reject anything else (including
+  // accidentally-published datetimes) so downstream parseIsoDate cannot
+  // produce an Invalid Date and crash the renderer.
+  const ISO_DATE = /^\d{4}-\d{2}-\d{2}$/
+  if (!ISO_DATE.test(start)) return null
+  const end = getTagValue(event.tags, 'end')
+  if (end && !ISO_DATE.test(end)) return null
+
   const participants: Participant[] = event.tags
     .filter(t => t[0] === 'p')
     .map(t => ({
@@ -197,7 +205,7 @@ export function parseCalendarDateEvent(event: NostrEvent): CalendarDateEvent | n
     content: event.content,
     image: getTagValue(event.tags, 'image'),
     start,
-    end: getTagValue(event.tags, 'end'),
+    end,
     location: getTagValue(event.tags, 'location'),
     geohash: getTagValue(event.tags, 'g'),
     hashtags: getTagValues(event.tags, 't'),