fix: convert calendar event times to user timezone in briefing

The briefing was formatting event start_dt directly in UTC instead of
converting to the user's local timezone. Also, the day_start/day_end
query window was naive (UTC), so events at the edges of the user's day
could be missed or included incorrectly.

Now reads user_timezone setting, uses it for today's date boundary and
for converting each event's start_dt before formatting.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/services/briefing_pipeline.py

@@ -8,6 +8,7 @@ import asyncio
 import hashlib
 import logging
 from datetime import date, datetime, timezone
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
 import httpx
 
@@ -129,7 +130,13 @@ async def _gather_internal(user_id: int) -> dict:
     from fabledassistant.services.projects import list_projects
     from fabledassistant.services.caldav import is_caldav_configured, list_events
 
-    today = date.today().isoformat()
+    tz_name = await get_setting(user_id, "user_timezone") or "UTC"
+    try:
+        user_tz = ZoneInfo(tz_name)
+    except ZoneInfoNotFoundError:
+        user_tz = ZoneInfo("UTC")
+
+    today = datetime.now(user_tz).date().isoformat()
 
     # Tasks: overdue, due today, high priority in-progress
     all_tasks: list[dict] = []
@@ -166,9 +173,9 @@ async def _gather_internal(user_id: int) -> dict:
     calendar_events: list[str] = []
     try:
         from fabledassistant.services.events import list_events as list_internal_events
-        today_date = date.today()
-        day_start = datetime(today_date.year, today_date.month, today_date.day, 0, 0, 0)
-        day_end = datetime(today_date.year, today_date.month, today_date.day, 23, 59, 59)
+        today_date = datetime.now(user_tz).date()
+        day_start = datetime(today_date.year, today_date.month, today_date.day, 0, 0, 0, tzinfo=user_tz)
+        day_end = datetime(today_date.year, today_date.month, today_date.day, 23, 59, 59, tzinfo=user_tz)
         internal_events = await list_internal_events(
             user_id=user_id, date_from=day_start, date_to=day_end
         )
@@ -176,7 +183,8 @@ async def _gather_internal(user_id: int) -> dict:
             if e.all_day:
                 time_str = "all day"
             elif e.start_dt:
-                time_str = e.start_dt.strftime("%-I:%M %p")
+                local_dt = e.start_dt.astimezone(user_tz) if e.start_dt.tzinfo else e.start_dt.replace(tzinfo=timezone.utc).astimezone(user_tz)
+                time_str = local_dt.strftime("%-I:%M %p")
             else:
                 time_str = "unknown time"
             calendar_events.append(f"{e.title} at {time_str}")