feat(core,app,android,cli,ios): sync the library and settings, verify a share before adding it

Sync carried only watch positions, so a second device started empty. The
per-installation history file now also carries per-key registers
(pstr-core::profile): every share with its link and custom password, the
playback, appearance and metadata settings, the TMDB key, hand-picked
matches and per-title track choices. Newer updated_at wins per key, a
removal travels as an empty register, and a first sync stamps at 0 so a
fresh install takes the library the other devices have instead of
overwriting it with defaults. Volume, mute and the device-only settings
(cache budget, Wi-Fi only, background audio, hardware decoding) stay out.
The secrets live only in the end-to-end encrypted Drive file, never in
shares.json. FORMAT_VERSION stays 1; an older build ignores the registers.

Adding a share stored it before opening the link, so a first failure left a
broken entry and every retry said "already configured". add_verified opens
the link first and stores nothing on failure, and only the new share is
crawled afterwards, so another broken share cannot fail the add.

Android drops picture-in-picture: the window sized the video wrongly and
background audio already covers leaving the app.

iOS sizes the Metal drawable on every layout, so the picture no longer
stretches after a rotation or a Split View resize. Settings show a save at
once rather than after the match run, and a failed save reverts and says
why. Both phone clients gain an activity banner naming what is running, and
the add-share, metadata and change-match forms show progress and errors in
place.

ios/ProtonStream/UI/TitleView.swift

@@ -465,6 +465,9 @@ struct ChangeMatchSheet: View {
     // Choosing fetches the entry's episodes too, which is a few requests.
     @State private var choosing = false
     @State private var options: [MatchRecord] = []
+    /// Said here rather than in the snackbar, which this sheet covers.
+    @State private var failure: String?
+    @State private var searched = false
 
     init(title: TitleRecord, onDone: @escaping () -> Void) {
         self.title = title
@@ -481,7 +484,17 @@ struct ChangeMatchSheet: View {
                 .buttonStyle(.accent)
                 .disabled(term.trimmingCharacters(in: .whitespaces).isEmpty || searching)
             if choosing {
-                Text("Fetching its episodes…").textStyle(.bodySmall).padding(.top, 8)
+                HStack(spacing: 12) {
+                    ProgressView().controlSize(.small).tint(scheme.primary)
+                    Text("Fetching its episodes…").textStyle(.bodySmall)
+                }
+                .padding(.top, 8)
+            }
+            if let failure {
+                Text(failure).foregroundStyle(scheme.error)
+            }
+            if !searching, options.isEmpty, searched {
+                Text("Nothing found. Try the title's original or English name.").textStyle(.bodySmall)
             }
             ForEach(options, id: \.remoteId) { option in
                 Button { choose(option) } label: {
@@ -503,7 +516,7 @@ struct ChangeMatchSheet: View {
                         try await model.run { try $0.forgetMatch(titleKey: title.key) }
                         changed()
                     } catch {
-                        model.reportError(error)
+                        failure = errorMessage(error)
                     }
                 }
             }
@@ -516,24 +529,27 @@ struct ChangeMatchSheet: View {
         let term = term
         guard !term.trimmingCharacters(in: .whitespaces).isEmpty, !searching else { return }
         searching = true
+        failure = nil
         Task {
             do {
                 options = try await NativeRuntime.engine().searchMatches(titleKey: title.key, term: term)
             } catch {
-                model.reportError(error)
+                failure = errorMessage(error)
             }
             searching = false
+            searched = true
         }
     }
 
     private func choose(_ option: MatchRecord) {
         choosing = true
+        failure = nil
         Task {
             do {
                 try await NativeRuntime.engine().chooseMatch(titleKey: title.key, found: option)
                 changed()
             } catch {
-                model.reportError(error)
+                failure = errorMessage(error)
             }
             choosing = false
         }