feat: initialize events app with calendars, slots, tickets, and internal API

Extract events/calendar functionality into standalone microservice:
- app.py and events_api.py from apps/events/
- Calendar blueprints (calendars, calendar, calendar_entries, calendar_entry, day, slots, slot, ticket_types, ticket_type)
- Templates for all calendar/event views including admin
- Dockerfile (APP_MODULE=app:app, IMAGE=events)
- entrypoint.sh (no Alembic - migrations managed by blog app)
- Gitea CI workflow for build and deploy

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

bp/calendar/services/adopt_session_entries_for_user.py

@@ -0,0 +1,24 @@
+from sqlalchemy import select, update
+from models.calendars import CalendarEntry
+from sqlalchemy import func
+
+async def adopt_session_entries_for_user(session, user_id: int, session_id: str | None) -> None:
+    if not session_id:
+        return
+    # (Optional) Mark any existing entries for this user as deleted to avoid duplicates
+    await session.execute(
+        update(CalendarEntry)
+        .where(CalendarEntry.deleted_at.is_(None), CalendarEntry.user_id == user_id)
+        .values(deleted_at=func.now())
+    )
+    # Reassign anonymous entries to the user
+    result = await session.execute(
+        select(CalendarEntry).where(
+            CalendarEntry.deleted_at.is_(None),
+            CalendarEntry.session_id == session_id
+        )
+    )
+    anon_entries = result.scalars().all()
+    for entry in anon_entries:
+        entry.user_id = user_id
+    # No commit here; caller will commit