feat(meta,app,android,ios,cli): film backdrops and logos from TMDB by id

TVDB has no films, so ani.zip has no fanart or logo for one, and most of
the titles in a real library with nothing wide to draw were films. ani.zip
does name the TMDB entry of every AniList match. With a TMDB key stored
and AniList chosen, an entry left without a backdrop or a logo is asked
for /{movie,tv}/{id}/images: one request, by id, so no title name goes to
TMDB. A bare backdrop and a PNG logo in the viewer's language are
preferred, and a failure there only costs the art.

The TMDB key field is now offered with either provider, labelled optional
with AniList. TMDB as the provider fetches its logo the same way, and
backdrops at w1280 rather than w780. A forced run re-enriches hand-picked
titles too, so saving a key and matching everything again reaches them.

ios/ProtonStream/App/AppModel.swift

@@ -637,8 +637,10 @@ final class AppModel {
     func saveMetadataSettings(enabled: Bool, provider: MetadataProvider, language: String, apiKey: String) async -> String? {
         do {
             metadataSettings = try await run { engine in
-                if provider == .tmdb, !apiKey.trimmingCharacters(in: .whitespaces).isEmpty {
-                    try engine.setMetadataApiKey(provider: provider, key: apiKey)
+                // TMDB's is the only key: the provider's with TMDB chosen, and
+                // film art's with AniList.
+                if !apiKey.trimmingCharacters(in: .whitespaces).isEmpty {
+                    try engine.setMetadataApiKey(provider: .tmdb, key: apiKey)
                 }
                 try engine.setMetadataSettings(settings: MetadataSettingsRecord(enabled: enabled, provider: provider, language: language, ready: true))
                 return try engine.metadataSettings()

ios/ProtonStream/UI/SettingsView.swift

@@ -329,12 +329,12 @@ private struct MetadataSettingsSheet: View {
                         .buttonStyle(option == provider ? ProtonButtonStyle(kind: .accent) : ProtonButtonStyle(kind: .edged))
                 }
             }
-            Text(provider == .aniList ? "Anime, and television from TVmaze; no account or API key required." : "Film and television; requires a free TMDB API key.")
+            Text(provider == .aniList ? "Anime, and television from TVmaze; no account or API key required. With a TMDB API key, films get TMDB's backdrops and logos, asked for by id alone." : "Film and television; requires a free TMDB API key.")
                 .textStyle(.bodySmall)
             if provider == .tmdb {
                 Field(label: "Language", text: $language)
-                Field(label: current.ready ? "TMDB API key (leave blank to keep)" : "TMDB API key", text: $apiKey, secret: true)
             }
+            Field(label: provider == .aniList ? "TMDB API key (optional)" : current.ready ? "TMDB API key (leave blank to keep)" : "TMDB API key", text: $apiKey, secret: true)
             if enabled, provider == .tmdb, !current.ready, apiKey.trimmingCharacters(in: .whitespaces).isEmpty {
                 Text("Enter a TMDB API key to save.").foregroundStyle(scheme.error)
             }