Neither search backend orders by *where* the query matched, so a mid-word hit
could outrank a prefix one — typing "parks" surfaced "Sparks of Love" above
"Parks and Recreation".
Add `domain/search_rank.rs`, which sorts by match position (prefix →
word-start → mid-word substring → no name match), then by media kind so a
container outranks its own contents. The sort is stable, so each backend's own
relevance still breaks ties it was never overruled on. `repository_search`
applies it to both the instant cache result and the merged cache+server union,
so the list does not reshuffle when server results land. Ranking lives in Rust
because "a better match" is domain vocabulary, not presentation.
On the frontend, the combined `tvShows` result group splits into separate
Shows and Episodes groups so a show no longer competes with its own episodes
for a slot, and a People group is added so searching an actor's name reaches
their bio. A stored `tvShows` order expands in place, keeping the position an
upgrading user chose for it.
