Add ``m.event_id`` (T109's nullable column from migration 0014) to
``search_all_memories``'s SELECT, propagate it through the route's
template context, and have ``search.html`` build result links as
``/chats/{chat_id}#turn-{event_id}`` — matching the ``id="turn-{event_id}"``
anchor that Phase 3.5 T86 stamps on each turn DOM node so the chat page
scrolls to the originating turn on load. Memory rows projected before
the 0014 migration ran read NULL ``event_id``; the template falls back
to a chat-level link in that case so we never emit ``#turn-None``.
Pre-existing tests that asserted on the bare ``href="/chats/{chat_id}"``
contract are updated to assert on the ``href="/chats/{chat_id}#turn-``
prefix to reflect the new deep-link.
Joseph Doherty