feat(core,app,android,ios): more like this and browse by genre, studio, person

pstr_core::discover scores every title against another by shared
director, studio, genres, leading tags and format, leaves out its own
franchise and keeps one title per other franchise. It drives a "More
like this" row under a title's episodes and, seeded by the title most
recently watched to the end, a "Because you watched" row on the library
of titles not yet started.

Genre chips on the title page now open a page of every title with that
genre, and the studios and director move from the line of facts onto
chips of their own that do the same. The desktop has a Browse page whose
back link returns to the title; Android and iOS show it over the library
pane. The bridge exposes more_like, browse and facet_kind.

Also moves a doc comment the My List commit left on the wrong function.

ios/ProtonStream/App/AppModel.swift

@@ -548,6 +548,22 @@ final class AppModel {
         }
     }
 
+    /// The keys of the titles most like `key`, best first; none if the engine
+    /// cannot say.
+    func moreLike(_ key: String) async -> [String] {
+        (try? await run { try $0.moreLike(key: key) }) ?? []
+    }
+
+    /// The keys of every title `facet` stands for, in library order.
+    func browse(_ facet: BrowseFacet) async -> [String] {
+        do {
+            return try await run { try $0.browse(facet: facet) }
+        } catch {
+            reportError(error)
+            return []
+        }
+    }
+
     // MARK: - Watch state
 
     /// Every episode of a title watched or unwatched, with an Undo: a whole