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.

crates/pstr-app/src/ui/account.rs

@@ -133,9 +133,10 @@ impl DriveBrowser {
 pub fn section(ui: &mut egui::Ui, panel: &mut AccountPanel, actions: &mut Vec<Action>) {
     ui::section(ui, "Proton account");
     ui.label(ui::muted(
-        "Optional. Signed in, your watch history is kept in your own Drive and every device \
-         resumes where another left off, and folders of your Drive — your files, other \
-         devices, what was shared with you — can be added to the library.",
+        "Optional. Signed in, your shares, settings and watch history are kept in your own \
+         Drive, so every device shows the same library and resumes where another left off, \
+         and folders of your Drive — your files, other devices, what was shared with you — \
+         can be added to the library.",
     ));
     ui.add_space(theme::space::L);
 
@@ -281,9 +282,11 @@ fn signed_in(
                 .strong(),
             );
             let status = match (&panel.sync_error, &panel.synced) {
-                (Some(error), _) => format!("Watch history did not sync: {error}"),
+                (Some(error), _) => format!("Did not sync: {error}"),
                 (None, Some((at, report))) => sync_line(*at, report, unix_now()),
-                (None, None) => "Watch history syncs with your Drive".to_owned(),
+                (None, None) => {
+                    "Library, settings and watch history sync through your Drive".to_owned()
+                }
             };
             ui.label(ui::muted(status));
         });