🔍 fix: Include Message-Matched Conversations in Sidebar Search (#15483)

* 🔍 fix: Include Message-Matched Conversations in Sidebar Search

- Union conversation and message index matches in getConvosByCursor
- Type searchMessages with SearchParams and SchemaWithMeiliMethods
- Inject searchMessages into createConversationMethods
- Bound sidebar Meili queries with 1000 limit and attributesToRetrieve
- Fall back to title-only matches when message search fails or is uninjected
- Escape filter user values in search queries

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(search): preserve original conversation keys in sidebar hits

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* 🔍 fix: reuse the loaded conversation model

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* 🔍 fix: type the loaded conversation search model

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>