Wires T93's `search_all_memories` service into a small read-only HTML
surface so users can find a memory across every chat in the database.
* `chat/web/search.py` (new): GET `/search?q=...` runs the FTS service
with k=50, hydrates each row with bot name + scene timestamp, and
renders `search.html`. Empty `q` short-circuits to no results so the
top-bar form can submit even with an empty input.
* `chat/templates/search.html` (new): empty-state placeholder, results
list with chat-level "Open chat" links (`/chats/{chat_id}` — memories
don't carry an event_id today, so no per-turn anchor).
* `chat/templates/layout.html`: append a small `<form>` to the rail
nav, additive only.
* `chat/app.py`: register `search_router` (additive import + include).
* `tests/test_search_ux.py`: 3 tests — multi-chat results, empty-query
placeholder, chat link.
Joseph Doherty